diff --git a/api/v1/submissions/PKPSubmissionController.php b/api/v1/submissions/PKPSubmissionController.php
index 9b8bb930dd8..97f1ef1001f 100644
--- a/api/v1/submissions/PKPSubmissionController.php
+++ b/api/v1/submissions/PKPSubmissionController.php
@@ -902,7 +902,7 @@ public function getParticipants(Request $illuminateRequest): JsonResponse
         $context = $request->getContext();
         $submission = $this->getAuthorizedContextObject(Application::ASSOC_TYPE_SUBMISSION);
         $args = $illuminateRequest->input();
-        $stageId = $args['stageId'] ?? null;
+        $stageId = $args['stageId'] ?? $illuminateRequest->route('stageId') !== null ? (int) $illuminateRequest->route('stageId') : null;
 
         if (!$submission || $submission->getData('contextId') !== $context->getId()) {
             return response()->json([
@@ -919,7 +919,7 @@ public function getParticipants(Request $illuminateRequest): JsonResponse
 
         $map = Repo::user()->getSchemaMap();
         foreach ($usersIterator as $user) {
-            $data[] = $map->summarizeReviewer($user);
+            $data[] = $map->summarizeReviewer($user, ['submission' => $submission, 'stageId' => $stageId]);
         }
 
         return response()->json($data, Response::HTTP_OK);
diff --git a/classes/stageAssignment/StageAssignment.php b/classes/stageAssignment/StageAssignment.php
index 7103657b4a1..04da0d97002 100644
--- a/classes/stageAssignment/StageAssignment.php
+++ b/classes/stageAssignment/StageAssignment.php
@@ -90,7 +90,7 @@ public function scopeWithStageIds(Builder $query, ?array $stageIds): Builder
     public function scopeWithSubmissionIds(Builder $query, ?array $submissionIds): Builder
     {
         return $query->when($submissionIds !== null, function ($query) use ($submissionIds) {
-            return $query->whereIn('submission_id', $submissionIds);
+            return $query->whereIn('stage_assignments.submission_id', $submissionIds);
         });
     }
 
@@ -142,7 +142,7 @@ public function scopeWithContextId(Builder $query, ?int $contextId): Builder
     {
         return $query->when($contextId !== null, function ($query) use ($contextId) {
             return $query->join('submissions', 'stage_assignments.submission_id', '=', 'submissions.submission_id')
-                        ->where('submissions.context_id', $contextId);
+                ->where('submissions.context_id', $contextId);
         });
     }
 }
diff --git a/classes/user/maps/Schema.php b/classes/user/maps/Schema.php
index 182e1accde8..30e960bc97e 100644
--- a/classes/user/maps/Schema.php
+++ b/classes/user/maps/Schema.php
@@ -17,8 +17,12 @@
 use Illuminate\Support\Enumerable;
 use PKP\db\DAORegistry;
 use PKP\plugins\Hook;
+use PKP\security\Role;
 use PKP\services\PKPSchemaService;
+use PKP\stageAssignment\StageAssignment;
 use PKP\user\User;
+use PKP\workflow\WorkflowStageDAO;
+use Submission;
 
 class Schema extends \PKP\core\maps\Schema
 {
@@ -51,9 +55,9 @@ public function summarize(User $item): array
      *
      * Includes properties with the apiSummary flag in the user schema.
      */
-    public function summarizeReviewer(User $item): array
+    public function summarizeReviewer(User $item, array $auxiliaryData = []): array
     {
-        return $this->mapByProperties(array_merge($this->getSummaryProps(), ['reviewsActive', 'reviewsCompleted', 'reviewsDeclined', 'reviewsCancelled', 'averageReviewCompletionDays', 'dateLastReviewAssignment', 'reviewerRating']), $item);
+        return $this->mapByProperties(array_merge($this->getSummaryProps(), ['reviewsActive', 'reviewsCompleted', 'reviewsDeclined', 'reviewsCancelled', 'averageReviewCompletionDays', 'dateLastReviewAssignment', 'reviewerRating']), $item, $auxiliaryData);
     }
 
     /**
@@ -98,9 +102,11 @@ public function summarizeManyReviewers(Enumerable $collection): Enumerable
     /**
      * Map schema properties of a user to an assoc array
      *
+     * @param array $auxiliaryData - Associative array used to provide supplementary data needed to populate properties on the response.
+     *
      * @hook UserSchema::getProperties::values [[$this, &$output, $user, $props]]
      */
-    protected function mapByProperties(array $props, User $user): array
+    protected function mapByProperties(array $props, User $user, array $auxiliaryData = []): array
     {
         $output = [];
 
@@ -180,6 +186,54 @@ protected function mapByProperties(array $props, User $user): array
                             }
                         }
                     }
+                    break;
+                case 'stageAssignments':
+                    $submission = $auxiliaryData['submission'];
+                    $stageId = $auxiliaryData['stageId'];
+
+                    if((!isset($submission) || !isset($stageId)) || (!($submission instanceof Submission) || !is_numeric($auxiliaryData['stageId']))) {
+                        $output['stageAssignments'] = [];
+                        break;
+                    }
+
+                    // Get User's stage assignments for submission.
+                    // Note:
+                    // - A User can potentially have multiple assignments for a submission.
+                    // - A User can potentially have multiple assignments for a stage of a submission.
+                    $stageAssignments = StageAssignment::withSubmissionIds([$submission->getId()])
+                        ->withStageIds($stageId ? [$stageId] : [])
+                        ->withUserId($user->getId())
+                        ->withContextId($this->context->getId())
+                        ->get();
+
+                    $results = [];
+
+                    foreach ($stageAssignments as  $stageAssignment /**@var StageAssignment  $stageAssignment*/) {
+                        // Get related user group info for stage assignment
+                        $userGroup = Repo::userGroup()->get($stageAssignment->userGroupId);
+
+                        // Only prepare data for non-reviewer participants
+                        if ($userGroup->getRoleId() !== Role::ROLE_ID_REVIEWER) {
+                            $entry = [
+                                'stageAssignmentId' => $stageAssignment->id,
+                                'stageAssignmentUserGroup' => $userGroup->getAllData(),
+                                'stageAssignmentStageId' => $stageId,
+                                'recommendOnly' => (bool)$stageAssignment->recommendOnly,
+                                'canChangeMetadata' => (bool)$stageAssignment->canChangeMetadata
+                            ];
+
+                            $workflowStageDao = DAORegistry::getDAO('WorkflowStageDAO'); /** @var WorkflowStageDAO $workflowStageDao */
+                            $entry['stageAssignmentStage'] = [
+                                'id' => $stageId,
+                                'label' => __($workflowStageDao->getTranslationKeyFromId($stageId)),
+                            ];
+
+                            $results[] = $entry;
+                        }
+
+                        $output['stageAssignments'] = $results;
+                    }
+
                     break;
                 default:
                     $output[$prop] = $user->getData($prop);
diff --git a/schemas/user.json b/schemas/user.json
index ee96b45233e..d10b7de76e8 100644
--- a/schemas/user.json
+++ b/schemas/user.json
@@ -290,6 +290,43 @@
 			"validation": [
 				"nullable"
 			]
+		},
+		"stageAssignments": {
+			"apiSummary": true,
+			"readOnly": true,
+			"type": "array",
+			"items": {
+				"type": "object",
+				"properties": {
+					"stageAssignmentId": {
+						"type": "integer"
+					},
+					"stageAssignmentUserGroup": {
+						"type": "object",
+						"$ref": "#/definitions/UserGroup"
+					},
+					"stageAssignmentStageId": {
+						"type": "integer"
+					},
+					"stageAssignmentStage": {
+						"type": "object",
+						"properties": {
+							"id": {
+								"type": "string"
+							},
+							"label": {
+								"type": "string"
+							}
+						}
+					},
+					"canChangeMetadata": {
+						"type": "boolean"
+					},
+					"recommendOnly": {
+						"type": "boolean"
+					}
+				}
+			}
 		}
 	}
 }