diff --git a/app/soapbox/entity-store/__tests__/reducer.test.ts b/app/soapbox/entity-store/__tests__/reducer.test.ts
index f43150b68..1cfc19697 100644
--- a/app/soapbox/entity-store/__tests__/reducer.test.ts
+++ b/app/soapbox/entity-store/__tests__/reducer.test.ts
@@ -5,6 +5,7 @@ import {
   entitiesFetchRequest,
   entitiesFetchSuccess,
   importEntities,
+  incrementEntities,
 } from '../actions';
 import reducer, { State } from '../reducer';
 import { createListState } from '../utils';
@@ -167,4 +168,42 @@ test('dismiss items', () => {
   expect(result.TestEntity!.store).toMatchObject(state.TestEntity!.store);
   expect([...result.TestEntity!.lists.yolo!.ids]).toEqual(['2']);
   expect(result.TestEntity!.lists.yolo!.state.totalCount).toBe(1);
+});
+
+test('increment items', () => {
+  const state: State = {
+    TestEntity: {
+      store: { '1': { id: '1' }, '2': { id: '2' }, '3': { id: '3' } },
+      lists: {
+        thingies: {
+          ids: new Set(['1', '2', '3']),
+          state: { ...createListState(), totalCount: 3 },
+        },
+      },
+    },
+  };
+
+  const action = incrementEntities('TestEntity', 'thingies', 1);
+  const result = reducer(state, action);
+
+  expect(result.TestEntity!.lists.thingies!.state.totalCount).toBe(4);
+});
+
+test('decrement items', () => {
+  const state: State = {
+    TestEntity: {
+      store: { '1': { id: '1' }, '2': { id: '2' }, '3': { id: '3' } },
+      lists: {
+        thingies: {
+          ids: new Set(['1', '2', '3']),
+          state: { ...createListState(), totalCount: 3 },
+        },
+      },
+    },
+  };
+
+  const action = incrementEntities('TestEntity', 'thingies', -1);
+  const result = reducer(state, action);
+
+  expect(result.TestEntity!.lists.thingies!.state.totalCount).toBe(2);
 });
\ No newline at end of file
diff --git a/app/soapbox/entity-store/actions.ts b/app/soapbox/entity-store/actions.ts
index 8f4783c94..c3ba25559 100644
--- a/app/soapbox/entity-store/actions.ts
+++ b/app/soapbox/entity-store/actions.ts
@@ -3,6 +3,7 @@ import type { Entity, EntityListState } from './types';
 const ENTITIES_IMPORT = 'ENTITIES_IMPORT' as const;
 const ENTITIES_DELETE = 'ENTITIES_DELETE' as const;
 const ENTITIES_DISMISS = 'ENTITIES_DISMISS' as const;
+const ENTITIES_INCREMENT = 'ENTITIES_INCREMENT' as const;
 const ENTITIES_FETCH_REQUEST = 'ENTITIES_FETCH_REQUEST' as const;
 const ENTITIES_FETCH_SUCCESS = 'ENTITIES_FETCH_SUCCESS' as const;
 const ENTITIES_FETCH_FAIL = 'ENTITIES_FETCH_FAIL' as const;
@@ -40,6 +41,15 @@ function dismissEntities(ids: Iterable<string>, entityType: string, listKey: str
   };
 }
 
+function incrementEntities(entityType: string, listKey: string, diff: number) {
+  return {
+    type: ENTITIES_INCREMENT,
+    entityType,
+    listKey,
+    diff,
+  };
+}
+
 function entitiesFetchRequest(entityType: string, listKey?: string) {
   return {
     type: ENTITIES_FETCH_REQUEST,
@@ -87,6 +97,7 @@ type EntityAction =
   ReturnType<typeof importEntities>
   | ReturnType<typeof deleteEntities>
   | ReturnType<typeof dismissEntities>
+  | ReturnType<typeof incrementEntities>
   | ReturnType<typeof entitiesFetchRequest>
   | ReturnType<typeof entitiesFetchSuccess>
   | ReturnType<typeof entitiesFetchFail>
@@ -96,6 +107,7 @@ export {
   ENTITIES_IMPORT,
   ENTITIES_DELETE,
   ENTITIES_DISMISS,
+  ENTITIES_INCREMENT,
   ENTITIES_FETCH_REQUEST,
   ENTITIES_FETCH_SUCCESS,
   ENTITIES_FETCH_FAIL,
@@ -103,6 +115,7 @@ export {
   importEntities,
   deleteEntities,
   dismissEntities,
+  incrementEntities,
   entitiesFetchRequest,
   entitiesFetchSuccess,
   entitiesFetchFail,
diff --git a/app/soapbox/entity-store/hooks/index.ts b/app/soapbox/entity-store/hooks/index.ts
index 09fe0c960..d113c505a 100644
--- a/app/soapbox/entity-store/hooks/index.ts
+++ b/app/soapbox/entity-store/hooks/index.ts
@@ -3,4 +3,5 @@ export { useEntity } from './useEntity';
 export { useEntityActions } from './useEntityActions';
 export { useCreateEntity } from './useCreateEntity';
 export { useDeleteEntity } from './useDeleteEntity';
-export { useDismissEntity } from './useDismissEntity';
\ No newline at end of file
+export { useDismissEntity } from './useDismissEntity';
+export { useIncrementEntity } from './useIncrementEntity';
\ No newline at end of file
diff --git a/app/soapbox/entity-store/hooks/useIncrementEntity.ts b/app/soapbox/entity-store/hooks/useIncrementEntity.ts
new file mode 100644
index 000000000..5f87fdea4
--- /dev/null
+++ b/app/soapbox/entity-store/hooks/useIncrementEntity.ts
@@ -0,0 +1,33 @@
+import { useAppDispatch } from 'soapbox/hooks';
+
+import { incrementEntities } from '../actions';
+
+import { parseEntitiesPath } from './utils';
+
+import type { ExpandedEntitiesPath } from './types';
+
+type IncrementFn<T> = (entityId: string) => Promise<T> | T;
+
+/**
+ * Increases (or decreases) the `totalCount` in the entity list by the specified amount.
+ * This only works if the API returns an `X-Total-Count` header and your components read it.
+ */
+function useIncrementEntity<T = unknown>(
+  expandedPath: ExpandedEntitiesPath,
+  diff: number,
+  incrementFn: IncrementFn<T>,
+) {
+  const { entityType, listKey } = parseEntitiesPath(expandedPath);
+  const dispatch = useAppDispatch();
+
+  return async function incrementEntity(entityId: string): Promise<void> {
+    try {
+      await incrementFn(entityId);
+      dispatch(incrementEntities(entityType, listKey, diff));
+    } catch (e) {
+      dispatch(incrementEntities(entityType, listKey, diff * -1));
+    }
+  };
+}
+
+export { useIncrementEntity };
\ No newline at end of file
diff --git a/app/soapbox/entity-store/reducer.ts b/app/soapbox/entity-store/reducer.ts
index 7559b66a7..b71fb812f 100644
--- a/app/soapbox/entity-store/reducer.ts
+++ b/app/soapbox/entity-store/reducer.ts
@@ -9,6 +9,7 @@ import {
   ENTITIES_FETCH_FAIL,
   EntityAction,
   ENTITIES_INVALIDATE_LIST,
+  ENTITIES_INCREMENT,
 } from './actions';
 import { createCache, createList, updateStore, updateList } from './utils';
 
@@ -108,6 +109,23 @@ const dismissEntities = (
   });
 };
 
+const incrementEntities = (
+  state: State,
+  entityType: string,
+  listKey: string,
+  diff: number,
+) => {
+  return produce(state, draft => {
+    const cache = draft[entityType] ?? createCache();
+    const list = cache.lists[listKey];
+
+    if (typeof list?.state?.totalCount === 'number') {
+      list.state.totalCount += diff;
+      draft[entityType] = cache;
+    }
+  });
+};
+
 const setFetching = (
   state: State,
   entityType: string,
@@ -146,6 +164,8 @@ function reducer(state: Readonly<State> = {}, action: EntityAction): State {
       return deleteEntities(state, action.entityType, action.ids, action.opts);
     case ENTITIES_DISMISS:
       return dismissEntities(state, action.entityType, action.ids, action.listKey);
+    case ENTITIES_INCREMENT:
+      return incrementEntities(state, action.entityType, action.listKey, action.diff);
     case ENTITIES_FETCH_SUCCESS:
       return importEntities(state, action.entityType, action.entities, action.listKey, action.newState, action.overwrite);
     case ENTITIES_FETCH_REQUEST:
diff --git a/app/soapbox/hooks/api/groups/useGroupMembershipRequests.ts b/app/soapbox/hooks/api/groups/useGroupMembershipRequests.ts
index cafea3601..560aef329 100644
--- a/app/soapbox/hooks/api/groups/useGroupMembershipRequests.ts
+++ b/app/soapbox/hooks/api/groups/useGroupMembershipRequests.ts
@@ -1,5 +1,5 @@
 import { Entities } from 'soapbox/entity-store/entities';
-import { useEntities } from 'soapbox/entity-store/hooks';
+import { useEntities, useIncrementEntity } from 'soapbox/entity-store/hooks';
 import { useApi } from 'soapbox/hooks/useApi';
 import { accountSchema } from 'soapbox/schemas';
 
@@ -15,17 +15,17 @@ function useGroupMembershipRequests(groupId: string) {
     { schema: accountSchema },
   );
 
-  function authorize(accountId: string) {
+  const authorize = useIncrementEntity(path, -1, (accountId: string) => {
     return api
       .post(`/api/v1/groups/${groupId}/membership_requests/${accountId}/authorize`)
       .then(invalidate);
-  }
+  });
 
-  function reject(accountId: string) {
+  const reject = useIncrementEntity(path, -1, (accountId: string) => {
     return api
       .post(`/api/v1/groups/${groupId}/membership_requests/${accountId}/reject`)
       .then(invalidate);
-  }
+  });
 
   return {
     accounts: entities,