diff --git a/packages/toolkit/src/entities/sorted_state_adapter.ts b/packages/toolkit/src/entities/sorted_state_adapter.ts
index 7731bd5ba7..c96f16380e 100644
--- a/packages/toolkit/src/entities/sorted_state_adapter.ts
+++ b/packages/toolkit/src/entities/sorted_state_adapter.ts
@@ -70,9 +70,14 @@ export function createSortedStateAdapter<T, Id extends EntityId>(
     newEntities = ensureEntitiesArray(newEntities)
 
     const existingKeys = new Set<Id>(existingIds ?? getCurrent(state.ids))
-
+    const addedKeys = new Set<Id>();
     const models = newEntities.filter(
-      (model) => !existingKeys.has(selectIdValue(model, selectId)),
+      (model) => {
+          const modelId = selectIdValue(model, selectId);
+          const notAdded = !addedKeys.has(modelId);
+          if (notAdded) addedKeys.add(modelId);
+          return !existingKeys.has(modelId) && notAdded;
+      }
     )
 
     if (models.length !== 0) {
diff --git a/packages/toolkit/src/entities/tests/sorted_state_adapter.test.ts b/packages/toolkit/src/entities/tests/sorted_state_adapter.test.ts
index d378449886..81ff44c409 100644
--- a/packages/toolkit/src/entities/tests/sorted_state_adapter.test.ts
+++ b/packages/toolkit/src/entities/tests/sorted_state_adapter.test.ts
@@ -588,6 +588,25 @@ describe('Sorted State Adapter', () => {
     })
   })
 
+  it('should work consistent with Unsorted State Adapter adding duplicate ids', () => {
+    const unsortedAdaptor = createEntityAdapter({
+      selectId: (book: BookModel) => book.id
+    });
+
+    const firstEntry = {id: AClockworkOrange.id, author: TheHobbit.author }
+    const secondEntry = {id: AClockworkOrange.id, title: 'Zack' }
+    const withNothingSorted = adapter.setAll(state, []);
+    const withNothingUnsorted = unsortedAdaptor.setAll(state, []);
+    const withOneSorted = adapter.addMany(withNothingSorted, [
+      { ...AClockworkOrange, ...firstEntry }, {...AClockworkOrange, ...secondEntry}
+    ])
+    const withOneUnsorted = adapter.addMany(withNothingUnsorted, [
+      { ...AClockworkOrange, ...firstEntry }, {...AClockworkOrange, ...secondEntry}
+    ])
+
+    expect(withOneSorted).toEqual(withOneUnsorted);
+  })
+
   it('should let you set many entities in the state when passing in a dictionary', () => {
     const changeWithoutAuthor = { id: TheHobbit.id, title: 'Silmarillion' }
     const withMany = adapter.setAll(state, [TheHobbit])
diff --git a/packages/toolkit/src/entities/tests/unsorted_state_adapter.test.ts b/packages/toolkit/src/entities/tests/unsorted_state_adapter.test.ts
index d7b551e63b..6249f5706d 100644
--- a/packages/toolkit/src/entities/tests/unsorted_state_adapter.test.ts
+++ b/packages/toolkit/src/entities/tests/unsorted_state_adapter.test.ts
@@ -89,6 +89,26 @@ describe('Unsorted State Adapter', () => {
     })
   })
 
+  it('should let you add the only first occurrence for duplicate ids', () => {
+    const firstEntry = {id: AClockworkOrange.id, author: TheHobbit.author }
+    const secondEntry = {id: AClockworkOrange.id, title: 'Zack' }
+    const withOne = adapter.setAll(state, [TheGreatGatsby])
+    const withMany = adapter.addMany(withOne, [
+      { ...AClockworkOrange, ...firstEntry }, {...AClockworkOrange, ...secondEntry}
+    ])
+
+    expect(withMany).toEqual({
+      ids: [TheGreatGatsby.id, AClockworkOrange.id],
+      entities: {
+        [TheGreatGatsby.id]: TheGreatGatsby,
+        [AClockworkOrange.id]: {
+          ...AClockworkOrange,
+          ...firstEntry,
+        },
+      },
+    })
+  })
+
   it('should remove existing and add new ones on setAll', () => {
     const withOneEntity = adapter.addOne(state, TheGreatGatsby)