diff --git a/api-generator/components/treeselect.js b/api-generator/components/treeselect.js
index f449f9ae3..b1a896b45 100644
--- a/api-generator/components/treeselect.js
+++ b/api-generator/components/treeselect.js
@@ -41,12 +41,6 @@ const TreeSelectProps = [
         default: "null",
         description: "Identifier of the underlying input element."
     },
-    {
-        name: "ariaLabelledBy",
-        type: "string",
-        default: "null",
-        description: "Establishes relationships between the component and label(s) where its value should be one or more element IDs."
-    },
     {
         name: "selectionMode",
         type: "string",
diff --git a/src/components/tree/Tree.vue b/src/components/tree/Tree.vue
index d7babe546..925e44c91 100755
--- a/src/components/tree/Tree.vue
+++ b/src/components/tree/Tree.vue
@@ -10,9 +10,9 @@
                 @keydown="onFilterKeydown" v-model="filterValue" />
             <span class="p-tree-filter-icon pi pi-search"></span>
         </div>
-        <div class="p-tree-wrapper" :style="{maxHeight: scrollHeight}">
-            <ul class="p-tree-container" role="tree">
-                <TreeNode v-for="node of valueToRender" :key="node.key" :node="node" :templates="$slots"
+        <div class="p-tree-wrapper" role="tree" :style="{maxHeight: scrollHeight}">
+            <ul class="p-tree-container" role="group">
+                <TreeNode v-for="(node, index) of valueToRender" :key="node.key" :node="node" :templates="$slots" :level="level + 1" :index="index"
                     :expandedKeys="d_expandedKeys" @node-toggle="onNodeToggle" @node-click="onNodeClick"
                     :selectionMode="selectionMode" :selectionKeys="selectionKeys" @checkbox-change="onCheckboxChange"></TreeNode>
             </ul>
@@ -79,6 +79,10 @@ export default {
         scrollHeight: {
             type: String,
             default: null
+        },
+        level: {
+            type: Number,
+            default: 0
         }
     },
     data() {
diff --git a/src/components/tree/TreeNode.vue b/src/components/tree/TreeNode.vue
index d36dcc1f4..ffcb9bd5a 100755
--- a/src/components/tree/TreeNode.vue
+++ b/src/components/tree/TreeNode.vue
@@ -1,5 +1,6 @@
 <template>
-    <li :class="containerClass">
+    <li :class="containerClass" role="treeitem" :aria-label="label(node)" :aria-selected="selected" :aria-expanded="expanded"
+        :aria-setsize="node.children ? node.children.length : 0" :aria-posinset="index + 1" :aria-level="level">
         <div :class="contentClass" tabindex="0" role="treeitem" :aria-expanded="expanded"
             @click="onClick" @keydown="onKeyDown" @touchend="onTouchEnd" :style="node.style">
             <button type="button" class="p-tree-toggler p-link" @click="toggle" tabindex="-1" v-ripple>
@@ -17,7 +18,7 @@
             </span>
         </div>
         <ul class="p-treenode-children" role="group" v-if="hasChildren && expanded">
-            <TreeNode v-for="childNode of node.children" :key="childNode.key" :node="childNode" :templates="templates"
+            <TreeNode v-for="childNode of node.children" :key="childNode.key" :node="childNode" :templates="templates" :level="level + 1"
                 :expandedKeys="expandedKeys" @node-toggle="onChildNodeToggle" @node-click="onChildNodeClick"
                 :selectionMode="selectionMode" :selectionKeys="selectionKeys"
                 @checkbox-change="propagateUp" />
@@ -52,6 +53,14 @@ export default {
         templates: {
             type: null,
             default: null
+        },
+        level: {
+            type: Number,
+            default: null
+        },
+        index: {
+            type: Number,
+            default: null
         }
     },
     nodeTouched: false,
@@ -92,9 +101,8 @@ export default {
         onKeyDown(event) {
             const nodeElement = event.target.parentElement;
 
-            switch (event.which) {
-                //down arrow
-                case 40:
+            switch (event.code) {
+                case 'ArrowDown':
                     var listElement = nodeElement.children[1];
                     if (listElement) {
                         this.focusNode(listElement.children[0]);
@@ -111,12 +119,9 @@ export default {
                             }
                         }
                     }
-
-                    event.preventDefault();
                 break;
 
-                //up arrow
-                case 38:
+                case 'ArrowUp':
                     if (nodeElement.previousElementSibling) {
                         this.focusNode(this.findLastVisibleDescendant(nodeElement.previousElementSibling));
                     }
@@ -126,28 +131,24 @@ export default {
                             this.focusNode(parentNodeElement);
                         }
                     }
-
-                    event.preventDefault();
                 break;
 
-                //right-left arrows
-                case 37:
-                case 39:
+                case 'ArrowRight':
+                case 'ArrowLeft':
                     this.$emit('node-toggle', this.node);
-
-                    event.preventDefault();
                 break;
 
-                //enter
-                case 13:
+                case 'Enter':
+                case 'Space':
                     this.onClick(event);
-                    event.preventDefault();
                 break;
 
                 default:
                     //no op
                 break;
             }
+
+            event.preventDefault();
         },
         toggleCheckbox() {
             let _selectionKeys = this.selectionKeys ? {...this.selectionKeys} : {};
diff --git a/src/components/treeselect/TreeSelect.d.ts b/src/components/treeselect/TreeSelect.d.ts
index 4d6428097..77c28239c 100644
--- a/src/components/treeselect/TreeSelect.d.ts
+++ b/src/components/treeselect/TreeSelect.d.ts
@@ -38,10 +38,6 @@ export interface TreeSelectProps {
      * Identifier of the underlying input element.
      */
     inputId?: string | undefined;
-    /**
-     * Establishes relationships between the component and label(s) where its value should be one or more element IDs.
-     */
-    ariaLabelledBy?: string | undefined;
     /**
      * Defines the selection mode.
      * @see TreeSelectSelectionModeType
diff --git a/src/components/treeselect/TreeSelect.vue b/src/components/treeselect/TreeSelect.vue
index 04558d5f8..f9d041654 100644
--- a/src/components/treeselect/TreeSelect.vue
+++ b/src/components/treeselect/TreeSelect.vue
@@ -1,8 +1,8 @@
 <template>
     <div ref="container" :class="containerClass" @click="onClick">
         <div class="p-hidden-accessible">
-            <input ref="focusInput" type="text" role="listbox" :id="inputId" readonly :disabled="disabled" @focus="onFocus" @blur="onBlur" @keydown="onKeyDown" :tabindex="tabindex"
-                aria-haspopup="true" :aria-expanded="overlayVisible" :aria-labelledby="ariaLabelledBy"/>
+            <input ref="focusInput" type="text" role="combobox" :id="inputId" readonly :disabled="disabled" :tabindex="tabindex" :aria-labelledby="ariaLabelledby" :aria-label="ariaLabel"
+                aria-haspopup="listbox" :aria-expanded="overlayVisible" :aria-controls="listId" @focus="onFocus($event)" @blur="onBlur($event)" @keydown="onKeyDown($event)" v-bind="inputProps" />
         </div>
         <div class="p-treeselect-label-container">
             <div :class="labelClass">
@@ -19,7 +19,7 @@
                 </slot>
             </div>
         </div>
-        <div class="p-treeselect-trigger">
+        <div class="p-treeselect-trigger" role="button" aria-haspopup="listbox" :aria-expanded="overlayVisible">
             <slot name="indicator">
                 <span class="p-treeselect-trigger-icon pi pi-chevron-down"></span>
             </slot>
@@ -29,10 +29,10 @@
                 <div :ref="overlayRef" v-if="overlayVisible" @click="onOverlayClick" :class="panelStyleClass">
                     <slot name="header" :value="modelValue" :options="options"></slot>
                     <div class="p-treeselect-items-wrapper" :style="{'max-height': scrollHeight}">
-                        <TSTree :value="options" :selectionMode="selectionMode" @update:selectionKeys="onSelectionChange" :selectionKeys="modelValue"
+                        <TSTree :id="listId" :value="options" :selectionMode="selectionMode" @update:selectionKeys="onSelectionChange" :selectionKeys="modelValue"
                             :expandedKeys="expandedKeys" @update:expandedKeys="onNodeToggle" :metaKeySelection="metaKeySelection"
                             @node-expand="$emit('node-expand', $event)" @node-collapse="$emit('node-collapse', $event)"
-                            @node-select="onNodeSelect" @node-unselect="onNodeUnselect" />
+                            @node-select="onNodeSelect" @node-unselect="onNodeUnselect" :level="0" />
                         <div v-if="emptyOptions" class="p-treeselect-empty-message">
                             <slot name="empty">{{emptyMessageText}}</slot>
                         </div>
@@ -45,7 +45,7 @@
 </template>
 
 <script>
-import {ConnectedOverlayScrollHandler,DomHandler,ZIndexUtils} from 'primevue/utils';
+import {ConnectedOverlayScrollHandler,DomHandler,ZIndexUtils,UniqueComponentId} from 'primevue/utils';
 import OverlayEventBus from 'primevue/overlayeventbus';
 import Tree from 'primevue/tree';
 import Ripple from 'primevue/ripple';
@@ -53,7 +53,7 @@ import Portal from 'primevue/portal';
 
 export default {
     name: 'TreeSelect',
-    emits: ['update:modelValue', 'before-show', 'before-hide', 'change', 'show', 'hide', 'node-select', 'node-unselect', 'node-expand', 'node-collapse'],
+    emits: ['update:modelValue', 'before-show', 'before-hide', 'change', 'show', 'hide', 'node-select', 'node-unselect', 'node-expand', 'node-collapse', 'focus', 'blur'],
     props: {
         modelValue: null,
         options: Array,
@@ -65,7 +65,7 @@ export default {
 		disabled: Boolean,
         tabindex: String,
         inputId: String,
-        ariaLabelledBy: null,
+        inputProps: null,
         selectionMode: {
             type: String,
             default: 'single'
@@ -89,6 +89,14 @@ export default {
         metaKeySelection: {
             type: Boolean,
             default: true
+        },
+        'aria-labelledby': {
+            type: String,
+			default: null
+        },
+        'aria-label': {
+            type: String,
+            default: null
         }
     },
     watch: {
@@ -143,11 +151,13 @@ export default {
             this.$emit('before-hide');
             this.overlayVisible = false;
         },
-        onFocus() {
+        onFocus(event) {
             this.focused = true;
+            this.$emit('focus', event);
         },
-        onBlur() {
+        onBlur(event) {
             this.focused = false;
+            this.$emit('blur', event);
         },
         onClick(event) {
             if (!this.disabled && (!this.overlay || !this.overlay.contains(event.target)) && !DomHandler.hasClass(event.target, 'p-treeselect-close')) {
@@ -178,37 +188,38 @@ export default {
             this.expandedKeys = keys;
         },
         onKeyDown(event) {
-            switch(event.which) {
-                //down
-                case 40:
-                    if (!this.overlayVisible && event.altKey) {
-                        this.show();
-                        event.preventDefault();
+            switch(event.code) {
+                case 'Down':
+                case 'ArrowDown':
+                    if (this.overlayVisible) {
+                        if (DomHandler.findSingle(this.overlay, '.p-highlight')) {
+                            DomHandler.findSingle(this.overlay, '.p-highlight').focus();
+                        }
+                        else DomHandler.findSingle(this.overlay, '.p-treenode').children[0].focus();
                     }
+                    else {
+                        this.show();
+                    }
+
+                    event.preventDefault();
                 break;
 
-                //space
-                case 32:
+                case 'Space':
+                case 'Enter':
                     if (!this.overlayVisible) {
                         this.show();
                         event.preventDefault();
                     }
                 break;
 
-                //enter and escape
-                case 13:
-                case 27:
+                case 'Escape':
+                case 'Tab':
                     if (this.overlayVisible) {
                         this.hide();
                         event.preventDefault();
                     }
                 break;
 
-                //tab
-                case 9:
-                    this.hide();
-                break;
-
                 default:
                 break;
             }
@@ -415,6 +426,9 @@ export default {
         },
         emptyOptions() {
             return !this.options || this.options.length === 0;
+        },
+        listId() {
+            return UniqueComponentId() + '_list';
         }
     },
     components: {
diff --git a/src/views/treeselect/TreeSelectDoc.vue b/src/views/treeselect/TreeSelectDoc.vue
index 09147b7c1..521925081 100644
--- a/src/views/treeselect/TreeSelectDoc.vue
+++ b/src/views/treeselect/TreeSelectDoc.vue
@@ -292,12 +292,6 @@ data() {
                         <td>null</td>
                         <td>Identifier of the underlying input element.</td>
                     </tr>
-                    <tr>
-                        <td>ariaLabelledBy</td>
-                        <td>string</td>
-                        <td>null</td>
-                        <td>Establishes relationships between the component and label(s) where its value should be one or more element IDs.</td>
-                    </tr>
                     <tr>
                         <td>selectionMode</td>
                         <td>string</td>
@@ -329,7 +323,7 @@ data() {
                         <td>comma</td>
                         <td>Defines how the selected items are displayed, valid values are "comma" and "chip".</td>
                     </tr>
-                     <tr>
+                    <tr>
                         <td>metaKeySelection</td>
                         <td>boolean</td>
                         <td>true</td>
@@ -448,7 +442,7 @@ data() {
                     <tr>
                         <td>footer</td>
                         <td>value: Value of the component <br />
-                           options: TreeNode options</td>
+                            options: TreeNode options</td>
                     </tr>
                     <tr>
                         <td>empty</td>
@@ -501,6 +495,100 @@ data() {
 			</table>
 		</div>
 
+        <h5>Accessibility</h5>
+        <DevelopmentSection>
+            <h6>Screen Reader</h6>
+            <p>Value to describe the component can either be provided with <i>aria-labelledby</i> or <i>aria-label</i> props. The treeselect element has a <i>combobox</i> role
+            in addition to <i>aria-haspopup</i> and <i>aria-expanded</i> attributes. The relation between the combobox and the popup is created with <i>aria-controls</i> that refers to the id of the popup.</p>
+            <p>The popup list has an id that refers to the <i>aria-controls</i> attribute of the <i>combobox</i> element and uses <i>tree</i> as the role. Each list item has a <i>treeitem</i> role along with <i>aria-label</i>, <i>aria-selected</i> and <i>aria-expanded</i> attributes. 
+            In checkbox selection, <i>aria-checked</i> is used instead of <i>aria-selected</i>. Checkbox and toggle icons are hidden from screen readers as their parent element with <i>treeitem</i> role and attributes are used instead for readers and keyboard support.
+            The container element of a treenode has the <i>group</i> role. The <i>aria-setsize</i>, <i>aria-posinset</i> and <i>aria-level</i> attributes are calculated implicitly and added to each treeitem.</p>
+
+<pre v-code><code>
+&lt;span id="dd1"&gt;Options&lt;/span&gt;
+&lt;TreeSelect aria-labelledby="dd1" /&gt;
+
+&lt;TreeSelect aria-label="Options" /&gt;
+
+</code></pre>
+
+            <h6>Closed State Keyboard Support</h6>
+            <div class="doc-tablewrapper">
+                <table class="doc-table">
+                    <thead>
+                        <tr>
+                            <th>Key</th>
+                            <th>Function</th>
+                        </tr>
+                    </thead>
+                    <tbody>
+                        <tr>
+                            <td><i>tab</i></td>
+                            <td>Moves focus to the treeselect element.</td>
+                        </tr>
+                        <tr>
+                            <td><i>space</i></td>
+                            <td>Opens the popup and moves visual focus to the selected treenode, if there is none then first treenode receives the focus.</td>
+                        </tr>
+                        <tr>
+                            <td><i>down arrow</i></td>
+                            <td>Opens the popup and moves visual focus to the selected option, if there is none then first option receives the focus.</td>
+                        </tr>
+                    </tbody>
+                </table>
+            </div>
+
+            <h6>Popup Keyboard Support</h6>
+            <div class="doc-tablewrapper">
+                <table class="doc-table">
+                    <thead>
+                        <tr>
+                            <th>Key</th>
+                            <th>Function</th>
+                        </tr>
+                    </thead>
+                    <tbody>
+                        <tr>
+                            <td><i>tab</i></td>
+                            <td>Moves focus to the next focusable element in the popup, if there is none then first focusable element receives the focus.</td>
+                        </tr>
+                        <tr>
+                            <td><i>shift</i> + <i>tab</i></td>
+                            <td>Moves focus to the previous focusable element in the popup, if there is none then last focusable element receives the focus.</td>
+                        </tr>
+                        <tr>
+                            <td><i>enter</i></td>
+                            <td>Selects the focused option, closes the popup if selection mode is single.</td>
+                        </tr>
+                        <tr>
+                            <td><i>space</i></td>
+                            <td>Selects the focused option, closes the popup if selection mode is single.</td>
+                        </tr>
+                        <tr>
+                            <td><i>escape</i></td>
+                            <td>Closes the popup, moves focus to the treeselect element.</td>
+                        </tr>
+                        <tr>
+                            <td><i>down arrow</i></td>
+                            <td>Moves focus to the next treenode.</td>
+                        </tr>
+                        <tr>
+                            <td><i>up arrow</i></td>
+                            <td>Moves focus to the previous treenode.</td>
+                        </tr>
+                        <tr>
+                            <td><i>right arrow</i></td>
+                            <td>If node is closed, opens the node otherwise moves focus to the first child node.</td>
+                        </tr>
+                        <tr>
+                            <td><i>left arrow</i></td>
+                            <td>If node is open, closes the node otherwise moves focus to the parent node.</td>
+                        </tr>
+                    </tbody>
+                </table>
+            </div>
+        </DevelopmentSection>
+
 		<h5>Dependencies</h5>
 		<p>None.</p>
     </AppDoc>