diff --git a/services/blob/src/http/handlers/holders.rs b/services/blob/src/http/handlers/holders.rs
--- a/services/blob/src/http/handlers/holders.rs
+++ b/services/blob/src/http/handlers/holders.rs
@@ -12,6 +12,79 @@
   holder: String,
 }
 
+#[derive(Deserialize, Debug)]
+#[serde(rename_all = "camelCase")]
+pub struct AssignHoldersPayload {
+  requests: Vec<BlobHashAndHolder>,
+}
+
+#[derive(Serialize, Debug)]
+#[serde(rename_all = "camelCase")]
+struct HolderAssignmentResult {
+  #[serde(flatten)]
+  request: BlobHashAndHolder,
+  success: bool,
+  data_exists: bool,
+  holder_already_exists: bool,
+}
+#[derive(Serialize, Debug)]
+#[serde(rename_all = "camelCase")]
+struct AssignHoldersResponse {
+  results: Vec<HolderAssignmentResult>,
+}
+
+#[instrument(name = "assign_multiple_holders", skip_all)]
+pub async fn assign_holders_handler(
+  service: web::Data<BlobService>,
+  payload: web::Json<AssignHoldersPayload>,
+) -> actix_web::Result<HttpResponse> {
+  use crate::database::DBError;
+  use crate::service::BlobServiceError;
+
+  let AssignHoldersPayload { requests } = payload.into_inner();
+  info!("Assign holder request for {} holders", requests.len());
+  validate_request(&requests)?;
+
+  let mut results = Vec::with_capacity(requests.len());
+
+  for item in requests {
+    let BlobHashAndHolder { blob_hash, holder } = &item;
+    let result = match service.assign_holder(blob_hash, holder).await {
+      Ok(data_exists) => HolderAssignmentResult {
+        request: item,
+        success: true,
+        data_exists,
+        holder_already_exists: false,
+      },
+      Err(BlobServiceError::DB(DBError::ItemAlreadyExists)) => {
+        let data_exists =
+          service.blob_hash_exists(blob_hash).await.unwrap_or(false);
+        HolderAssignmentResult {
+          request: item,
+          success: true,
+          data_exists,
+          holder_already_exists: true,
+        }
+      }
+      Err(err) => {
+        warn!("Holder assignment error: {:?}", err);
+        let data_exists =
+          service.blob_hash_exists(blob_hash).await.unwrap_or(false);
+        HolderAssignmentResult {
+          request: item,
+          success: false,
+          data_exists,
+          holder_already_exists: false,
+        }
+      }
+    };
+    results.push(result);
+  }
+
+  let response = AssignHoldersResponse { results };
+  Ok(HttpResponse::Ok().json(web::Json(response)))
+}
+
 #[derive(Deserialize, Debug)]
 #[serde(rename_all = "camelCase")]
 pub struct RemoveHoldersPayload {
diff --git a/services/blob/src/http/mod.rs b/services/blob/src/http/mod.rs
--- a/services/blob/src/http/mod.rs
+++ b/services/blob/src/http/mod.rs
@@ -48,6 +48,7 @@
       .service(
         web::resource("/holders")
           .wrap(auth_middleware)
+          .route(web::post().to(handlers::holders::assign_holders_handler))
           .route(web::delete().to(handlers::holders::remove_holders_handler)),
       )
   })
diff --git a/services/blob/src/service.rs b/services/blob/src/service.rs
--- a/services/blob/src/service.rs
+++ b/services/blob/src/service.rs
@@ -282,6 +282,19 @@
     Ok(())
   }
 
+  pub async fn blob_hash_exists(
+    &self,
+    blob_hash: impl Into<String>,
+  ) -> BlobServiceResult<bool> {
+    match self.db.get_blob_item(blob_hash).await {
+      Ok(item) => Ok(item.is_some()),
+      Err(err) => {
+        warn!("Failed to check if blob exists: {err:?}");
+        Err(err.into())
+      }
+    }
+  }
+
   pub async fn perform_cleanup(&self) -> anyhow::Result<()> {
     info!("Starting cleanup...");
     // 1. Fetch blobs and holders marked as "unchecked"