diff --git a/src/entity-manager/MongoEntityManager.ts b/src/entity-manager/MongoEntityManager.ts
index 2e5748a836..87642e02ff 100644
--- a/src/entity-manager/MongoEntityManager.ts
+++ b/src/entity-manager/MongoEntityManager.ts
@@ -133,10 +133,21 @@ export class MongoEntityManager extends EntityManager {
         const objectIdInstance = PlatformTools.load("mongodb").ObjectID;
         query["_id"] = {
             $in: ids.map(id => {
-                if (id instanceof objectIdInstance)
-                    return id;
+                if (typeof id === "string") {
+                    return new objectIdInstance(id);
+                }
 
-                return id[metadata.objectIdColumn!.propertyName];
+                if (typeof id === "object") {
+                    if (id instanceof objectIdInstance) {
+                        return id;
+                    }
+
+                    const propertyName = metadata.objectIdColumn!.propertyName;
+
+                    if (id[propertyName] instanceof objectIdInstance) {
+                        return id[propertyName];
+                    }
+                }
             })
         };
 
diff --git a/test/functional/mongodb/basic/mongo-repository/mongo-repository.ts b/test/functional/mongodb/basic/mongo-repository/mongo-repository.ts
index 11abe9579e..c68581eec0 100644
--- a/test/functional/mongodb/basic/mongo-repository/mongo-repository.ts
+++ b/test/functional/mongodb/basic/mongo-repository/mongo-repository.ts
@@ -86,6 +86,26 @@ describe("mongodb > MongoRepository", () => {
         loadedPosts[0].text.should.be.equal("Everything about post #1");
 
     })));
+  
+    it("should be able to use findByIds with both objectId and strings", () => Promise.all(connections.map(async connection => {
+        const postRepository = connection.getMongoRepository(Post);
+
+        // save few posts
+        const firstPost = new Post();
+        firstPost.title = "Post #1";
+        firstPost.text = "Everything about post #1";
+        await postRepository.save(firstPost);
+
+        const secondPost = new Post();
+        secondPost.title = "Post #2";
+        secondPost.text = "Everything about post #2";
+        await postRepository.save(secondPost);
+
+        expect(await postRepository.findByIds([ firstPost.id ])).to.have.length(1);
+        expect(await postRepository.findByIds([ firstPost.id.toHexString() ])).to.have.length(1);
+        expect(await postRepository.findByIds([ { id: firstPost.id } ])).to.have.length(1);
+        expect(await postRepository.findByIds([ undefined ])).to.have.length(0);
+    })));
 
     // todo: cover other methods as well
     it("should be able to save and update mongo entities", () => Promise.all(connections.map(async connection => {