diff --git a/api/admin/asset.go b/api/admin/asset.go
index f693171..8bf18a7 100644
--- a/api/admin/asset.go
+++ b/api/admin/asset.go
@@ -123,12 +123,13 @@ type QualityAnalysisResult struct {
 
 // RelatedComplementaryAssetResult contains the details about a related complementary asset.
 type RelatedComplementaryAssetResult struct {
-	AssetID           string `json:"asset_id"`
-	PublicID          string `json:"public_id"`
-	ResourceType      string `json:"resource_type"`
-	Type              string `json:"type"`
-	Status            string `json:"status"`
-	ComplementaryType string `json:"complementary_type"`
+	AssetID           string                 `json:"asset_id"`
+	PublicID          string                 `json:"public_id"`
+	ResourceType      string                 `json:"resource_type"`
+	Type              string                 `json:"type"`
+	Status            string                 `json:"status"`
+	ComplementaryType string                 `json:"complementary_type"`
+	Metadata          map[string]interface{} `json:"metadata"`
 }
 
 // AccessibilityAnalysisResult contains the details about accessibility analysis.
diff --git a/api/admin/assets.go b/api/admin/assets.go
index 94f4625..985ae11 100644
--- a/api/admin/assets.go
+++ b/api/admin/assets.go
@@ -454,9 +454,10 @@ func (a *API) DeleteRelatedAssetsByAssetIDs(ctx context.Context, params DeleteRe
 
 // RelatedComplementaryAssetsByAssetIDsParams are the parameters for AddRelatedComplementaryAssetsByAssetIDs.
 type RelatedComplementaryAssetsByAssetIDsParams struct {
-	AssetID           string   `json:"-"`
-	RelatedAssetIDs   []string `json:"related_asset_ids"`
-	ComplementaryType string   `json:"complementary_type"`
+	AssetID           string                 `json:"-"`
+	RelatedAssetIDs   []string               `json:"related_asset_ids"`
+	ComplementaryType string                 `json:"complementary_type"`
+	Metadata          map[string]interface{} `json:"metadata,omitempty"`
 }
 
 // AddRelatedComplementaryAssetsByAssetIDs relates an asset to other complementary assets by asset IDs.
diff --git a/api/admin/assets_acceptance_test.go b/api/admin/assets_acceptance_test.go
index dbabbef..f5eca0b 100644
--- a/api/admin/assets_acceptance_test.go
+++ b/api/admin/assets_acceptance_test.go
@@ -1263,13 +1263,16 @@ func getAddRelatedComplementaryAssetsByAssetIDsTestCases() []AdminAPIAcceptanceT
 
 	var testCases []AdminAPIAcceptanceTestCase
 
-	params := fmt.Sprintf("{\"related_asset_ids\":[\"%s\",\"%s\"],\"complementary_type\":\"complementary_type\"}", cldtest.AssetID2, cldtest.AssetID3)
+	params := fmt.Sprintf("{\"related_asset_ids\":[\"%s\",\"%s\"],\"complementary_type\":\"complementary_type\",\"metadata\":{\"test_value\":\"a string\"}}", cldtest.AssetID2, cldtest.AssetID3)
 	addRelatedComplementaryAssetsByAssetIDsTestCases := []addRelatedComplementaryAssetsByAssetIDsTestCase{
 		{
 			requestParams: admin.RelatedComplementaryAssetsByAssetIDsParams{
 				AssetID:           cldtest.AssetID,
 				RelatedAssetIDs:   []string{cldtest.AssetID2, cldtest.AssetID3},
 				ComplementaryType: "complementary_type",
+				Metadata: map[string]interface{}{
+					"test_value": "a string",
+				},
 			},
 			uri:            "/resources/related_complementary_assets/" + cldtest.AssetID,
 			expectedParams: &params,