diff --git a/packages/toolkit/src/entities/slice_creator.ts b/packages/toolkit/src/entities/slice_creator.ts
index e9485f573e..86ad9e5e30 100644
--- a/packages/toolkit/src/entities/slice_creator.ts
+++ b/packages/toolkit/src/entities/slice_creator.ts
@@ -6,8 +6,9 @@ import type {
 } from '@reduxjs/toolkit'
 import type { PayloadAction } from '../createAction'
 import { reducerCreator, type CaseReducerDefinition } from '../createSlice'
-import type { CastAny, WithRequiredProp } from '../tsHelpers'
+import type { WithRequiredProp } from '../tsHelpers'
 import type {
+  Update,
   EntityAdapter,
   EntityId,
   EntityState,
@@ -34,13 +35,11 @@ type EntityReducers<
   > as `${K}${Capitalize<K extends `${string}One` ? Single : Plural>}`]: EntityStateAdapter<
     T,
     Id
-  >[K] extends infer Method
-    ? Method extends CaseReducer<any, PayloadAction>
-      ? CaseReducerDefinition<State, PayloadAction>
-      : Method extends CaseReducer<any, PayloadAction<infer Payload>>
-        ? CaseReducerDefinition<State, PayloadAction<Payload>>
-        : never
-    : never
+  >[K] extends (state: any) => any
+    ? CaseReducerDefinition<State, PayloadAction>
+    : EntityStateAdapter<T, Id>[K] extends CaseReducer<any, infer A>
+      ? CaseReducerDefinition<State, A>
+      : never
 }
 
 export interface EntityMethodsCreatorConfig<
@@ -50,7 +49,7 @@ export interface EntityMethodsCreatorConfig<
   Single extends string,
   Plural extends string,
 > {
-  selectEntityState?: (state: CastAny<State, unknown>) => EntityState<T, Id>
+  selectEntityState?: (state: State) => EntityState<T, Id>
   name?: Single
   pluralName?: Plural
 }
@@ -104,49 +103,56 @@ declare module '@reduxjs/toolkit' {
   }
 }
 
-export const entityMethodsCreator: ReducerCreator<
-  typeof entityMethodsCreatorType
-> = {
+export const entityMethodsCreator = {
   type: entityMethodsCreatorType,
-  create(
-    adapter,
+  create<
+    T,
+    Id extends EntityId,
+    State = EntityState<T, Id>,
+    Single extends string = '',
+    Plural extends string = DefaultPlural<Single>,
+  >(
+    adapter: EntityAdapter<T, Id>,
     {
-      selectEntityState = (state) => state as EntityState<any, any>,
-      // template literal computed keys don't keep their type if there's an unresolved generic
-      // so we cast to some intermediate type to at least check we're using the right variables in the right places
-      name = '' as 's',
-      pluralName = name && (`${name}s` as 'p'),
-    }: EntityMethodsCreatorConfig<any, any, any, 's', 'p'> = {},
-  ): EntityReducers<any, any, any, 's', 'p'> {
+      selectEntityState = (state) => state as EntityState<T, Id>,
+      name: nameParam = '' as Single,
+      pluralName: pluralParam = (nameParam && `${nameParam}s`) as Plural,
+    }: EntityMethodsCreatorConfig<T, Id, State, Single, Plural> = {},
+  ): EntityReducers<T, Id, State, Single, Plural> {
+    // template literal computed keys don't keep their type if there's an unresolved generic
+    // so we cast to some intermediate type to at least check we're using the right variables in the right places
+
+    const name = nameParam as 's'
+    const pluralName = pluralParam as 'p'
     const reducer = reducerCreator.create
     return {
-      [`addOne${capitalize(name)}` as const]: reducer<any>((state, action) => {
+      [`addOne${capitalize(name)}` as const]: reducer<T>((state, action) => {
         adapter.addOne(selectEntityState(state), action.payload)
       }),
-      [`addMany${capitalize(pluralName)}` as const]: reducer<any>(
-        (state, action) => {
-          adapter.addMany(selectEntityState(state), action.payload)
-        },
-      ),
-      [`setOne${capitalize(name)}` as const]: reducer<any>((state, action) => {
+      [`addMany${capitalize(pluralName)}` as const]: reducer<
+        readonly T[] | Record<Id, T>
+      >((state, action) => {
+        adapter.addMany(selectEntityState(state), action.payload)
+      }),
+      [`setOne${capitalize(name)}` as const]: reducer<T>((state, action) => {
         adapter.setOne(selectEntityState(state), action.payload)
       }),
-      [`setMany${capitalize(pluralName)}` as const]: reducer<any>(
-        (state, action) => {
-          adapter.setMany(selectEntityState(state), action.payload)
-        },
-      ),
-      [`setAll${capitalize(pluralName)}` as const]: reducer<any>(
-        (state, action) => {
-          adapter.setAll(selectEntityState(state), action.payload)
-        },
-      ),
-      [`removeOne${capitalize(name)}` as const]: reducer<any>(
+      [`setMany${capitalize(pluralName)}` as const]: reducer<
+        readonly T[] | Record<Id, T>
+      >((state, action) => {
+        adapter.setMany(selectEntityState(state), action.payload)
+      }),
+      [`setAll${capitalize(pluralName)}` as const]: reducer<
+        readonly T[] | Record<Id, T>
+      >((state, action) => {
+        adapter.setAll(selectEntityState(state), action.payload)
+      }),
+      [`removeOne${capitalize(name)}` as const]: reducer<Id>(
         (state, action) => {
           adapter.removeOne(selectEntityState(state), action.payload)
         },
       ),
-      [`removeMany${capitalize(pluralName)}` as const]: reducer<any>(
+      [`removeMany${capitalize(pluralName)}` as const]: reducer<readonly Id[]>(
         (state, action) => {
           adapter.removeMany(selectEntityState(state), action.payload)
         },
@@ -154,26 +160,24 @@ export const entityMethodsCreator: ReducerCreator<
       [`removeAll${capitalize(pluralName)}` as const]: reducer((state) => {
         adapter.removeAll(selectEntityState(state))
       }),
-      [`upsertOne${capitalize(name)}` as const]: reducer<any>(
-        (state, action) => {
-          adapter.upsertOne(selectEntityState(state), action.payload)
-        },
-      ),
-      [`upsertMany${capitalize(pluralName)}` as const]: reducer<any>(
-        (state, action) => {
-          adapter.upsertMany(selectEntityState(state), action.payload)
-        },
-      ),
-      [`updateOne${capitalize(name)}` as const]: reducer<any>(
+      [`upsertOne${capitalize(name)}` as const]: reducer<T>((state, action) => {
+        adapter.upsertOne(selectEntityState(state), action.payload)
+      }),
+      [`upsertMany${capitalize(pluralName)}` as const]: reducer<
+        readonly T[] | Record<Id, T>
+      >((state, action) => {
+        adapter.upsertMany(selectEntityState(state), action.payload)
+      }),
+      [`updateOne${capitalize(name)}` as const]: reducer<Update<T, Id>>(
         (state, action) => {
           adapter.updateOne(selectEntityState(state), action.payload)
         },
       ),
-      [`updateMany${capitalize(pluralName)}` as const]: reducer<any>(
-        (state, action) => {
-          adapter.updateMany(selectEntityState(state), action.payload)
-        },
-      ),
-    }
+      [`updateMany${capitalize(pluralName)}` as const]: reducer<
+        readonly Update<T, Id>[]
+      >((state, action) => {
+        adapter.updateMany(selectEntityState(state), action.payload)
+      }),
+    } satisfies EntityReducers<T, Id, State, 's', 'p'> as any
   },
-}
+} satisfies ReducerCreator<typeof entityMethodsCreatorType>