diff --git a/packages/postgrest-core/src/mutate-item.ts b/packages/postgrest-core/src/mutate-item.ts
index b9025ce5..18361f1b 100644
--- a/packages/postgrest-core/src/mutate-item.ts
+++ b/packages/postgrest-core/src/mutate-item.ts
@@ -23,6 +23,7 @@ export const mutateOperation = <Type extends Record<string, unknown>>(
   primaryKeys: (keyof Type)[],
   filter: Pick<PostgrestFilter<Type>, 'apply'>,
   orderBy?: OrderDefinition[],
+  transformer?: (v: Type) => Type,
 ) => {
   // find item
   const itemIdx = currentData.findIndex((oldItem) =>
@@ -52,7 +53,11 @@ export const mutateOperation = <Type extends Record<string, unknown>>(
 
   // check that new item is still a valid member of the list and has all required paths
   if (filter.apply(newItem)) {
-    currentData.splice(newItemIdx, 0, newItem);
+    currentData.splice(
+      newItemIdx,
+      0,
+      transformer ? transformer(newItem) : newItem,
+    );
   }
 
   return currentData;
@@ -64,6 +69,7 @@ export type MutateItemOperation<Type extends Record<string, unknown>> = {
   input: Partial<Type>;
   mutate: (current: Type) => Type;
   primaryKeys: (keyof Type)[];
+  transformer?: (v: Type) => Type;
 } & RevalidateOpts<Type>;
 
 export type MutateItemCache<KeyType, Type extends Record<string, unknown>> = {
@@ -113,6 +119,7 @@ export const mutateItem = async <KeyType, Type extends Record<string, unknown>>(
     schema,
     table,
     primaryKeys,
+    transformer,
   } = op;
   const { cacheKeys, decode, getPostgrestFilter, mutate, revalidate } = cache;
 
@@ -165,6 +172,7 @@ export const mutateItem = async <KeyType, Type extends Record<string, unknown>>(
                     primaryKeys,
                     filter,
                     orderBy,
+                    transformer,
                   ),
                   currentData,
                   limit,
@@ -178,6 +186,7 @@ export const mutateItem = async <KeyType, Type extends Record<string, unknown>>(
                     primaryKeys,
                     filter,
                     orderBy,
+                    transformer,
                   ),
                   limit,
                 );
@@ -207,6 +216,7 @@ export const mutateItem = async <KeyType, Type extends Record<string, unknown>>(
                   primaryKeys,
                   filter,
                   orderBy,
+                  transformer,
                 );
 
                 return {
diff --git a/packages/postgrest-core/src/upsert-item.ts b/packages/postgrest-core/src/upsert-item.ts
index dcc57a20..3567e071 100644
--- a/packages/postgrest-core/src/upsert-item.ts
+++ b/packages/postgrest-core/src/upsert-item.ts
@@ -30,6 +30,7 @@ export const upsert = <Type extends Record<string, unknown>>(
   filter: Pick<PostgrestFilter<Type>, 'apply'>,
   mergeFn?: MergeFn<Type>,
   orderBy?: OrderDefinition[],
+  transformer?: (v: Type) => Type,
 ) => {
   const merge = mergeFn ?? (mergeAnything as MergeFn<Type>);
 
@@ -59,7 +60,11 @@ export const upsert = <Type extends Record<string, unknown>>(
 
   // check that new item is still a valid member of the list and has all required paths
   if (filter.apply(newItem)) {
-    currentData.splice(newItemIdx, 0, newItem);
+    currentData.splice(
+      newItemIdx,
+      0,
+      transformer ? transformer(newItem) : newItem,
+    );
   }
 
   return currentData;
@@ -71,6 +76,7 @@ export type UpsertItemOperation<Type extends Record<string, unknown>> = {
   input: Type;
   primaryKeys: (keyof Type)[];
   merge?: (current: Type, input: Type) => Type;
+  transformer?: (v: Type) => Type;
 } & RevalidateOpts<Type>;
 
 export type UpsertItemCache<KeyType, Type extends Record<string, unknown>> = {
@@ -118,6 +124,7 @@ export const upsertItem = async <KeyType, Type extends Record<string, unknown>>(
     schema,
     table,
     primaryKeys,
+    transformer,
   } = op;
   const { cacheKeys, decode, getPostgrestFilter, mutate, revalidate } = cache;
 
@@ -167,6 +174,7 @@ export const upsertItem = async <KeyType, Type extends Record<string, unknown>>(
                     filter,
                     merge,
                     orderBy,
+                    transformer,
                   ),
                   currentData,
                   limit,
@@ -180,6 +188,7 @@ export const upsertItem = async <KeyType, Type extends Record<string, unknown>>(
                     filter,
                     merge,
                     orderBy,
+                    transformer,
                   ),
                   limit,
                 );
@@ -209,6 +218,7 @@ export const upsertItem = async <KeyType, Type extends Record<string, unknown>>(
                   filter,
                   merge,
                   orderBy,
+                  transformer,
                 );
 
                 return {
diff --git a/packages/postgrest-react-query/src/mutate/use-insert-mutation.ts b/packages/postgrest-react-query/src/mutate/use-insert-mutation.ts
index 4de12f06..bd993a2f 100644
--- a/packages/postgrest-react-query/src/mutate/use-insert-mutation.ts
+++ b/packages/postgrest-react-query/src/mutate/use-insert-mutation.ts
@@ -37,7 +37,7 @@ function useInsertMutation<
   opts?: Omit<
     UsePostgrestMutationOpts<S, T, RelationName, Re, 'Insert', Q, R>,
     'mutationFn'
-  >,
+  > & { transformer?: (v: T['Row']) => Record<string, unknown> },
 ) {
   const queriesForTable = useQueriesForTableLoader(getTable(qb));
   const upsertItem = useUpsertItem({
diff --git a/packages/postgrest-react-query/src/mutate/use-update-mutation.ts b/packages/postgrest-react-query/src/mutate/use-update-mutation.ts
index 419743c1..e14106c5 100644
--- a/packages/postgrest-react-query/src/mutate/use-update-mutation.ts
+++ b/packages/postgrest-react-query/src/mutate/use-update-mutation.ts
@@ -36,7 +36,7 @@ function useUpdateMutation<
   opts?: Omit<
     UsePostgrestMutationOpts<S, T, RelationName, Re, 'UpdateOne', Q, R>,
     'mutationFn'
-  >,
+  > & { transformer?: (v: T['Row']) => Record<string, unknown> },
 ) {
   const queriesForTable = useQueriesForTableLoader(getTable(qb));
   const upsertItem = useUpsertItem({
diff --git a/packages/postgrest-react-query/src/mutate/use-upsert-mutation.ts b/packages/postgrest-react-query/src/mutate/use-upsert-mutation.ts
index 8501e2fa..f3c64e45 100644
--- a/packages/postgrest-react-query/src/mutate/use-upsert-mutation.ts
+++ b/packages/postgrest-react-query/src/mutate/use-upsert-mutation.ts
@@ -37,7 +37,7 @@ function useUpsertMutation<
   opts?: Omit<
     UsePostgrestMutationOpts<S, T, RelationName, Re, 'Upsert', Q, R>,
     'mutationFn'
-  >,
+  > & { transformer?: (v: T['Row']) => Record<string, unknown> },
 ) {
   const queriesForTable = useQueriesForTableLoader(getTable(qb));
   const upsertItem = useUpsertItem({
diff --git a/packages/postgrest-react-query/src/query/build-query-opts.ts b/packages/postgrest-react-query/src/query/build-query-opts.ts
index 1aee911a..bbc3089e 100644
--- a/packages/postgrest-react-query/src/query/build-query-opts.ts
+++ b/packages/postgrest-react-query/src/query/build-query-opts.ts
@@ -8,13 +8,23 @@ import type { UseQueryOptions as UseReactQueryOptions } from '@tanstack/react-qu
 
 import { encode } from '../lib/key';
 
-export function buildQueryOpts<Result>(
+export function buildQueryOpts<Result, TransformedResult = Result>(
   query: PromiseLike<AnyPostgrestResponse<Result>>,
   config?: Omit<
-    UseReactQueryOptions<AnyPostgrestResponse<Result>, PostgrestError>,
+    UseReactQueryOptions<
+      AnyPostgrestResponse<TransformedResult>,
+      PostgrestError
+    >,
     'queryKey' | 'queryFn'
-  >,
-): UseReactQueryOptions<AnyPostgrestResponse<Result>, PostgrestError> {
+  > & {
+    transformer?: (
+      data: AnyPostgrestResponse<Result>['data'],
+    ) => TransformedResult;
+  },
+): UseReactQueryOptions<
+  AnyPostgrestResponse<TransformedResult>,
+  PostgrestError
+> {
   return {
     queryKey: encode<Result>(query, false),
     queryFn: async ({ signal }) => {
@@ -24,7 +34,14 @@ export function buildQueryOpts<Result>(
       if (isPostgrestBuilder(query)) {
         query = query.throwOnError();
       }
-      return await query;
+      const result = await query;
+      if (config?.transformer && result.error === null) {
+        return {
+          ...result,
+          data: config.transformer(result.data),
+        };
+      }
+      return result as AnyPostgrestResponse<TransformedResult>;
     },
     ...config,
   };
diff --git a/packages/postgrest-react-query/src/query/use-query.ts b/packages/postgrest-react-query/src/query/use-query.ts
index e83aa7a5..7dcfb87e 100644
--- a/packages/postgrest-react-query/src/query/use-query.ts
+++ b/packages/postgrest-react-query/src/query/use-query.ts
@@ -76,65 +76,90 @@ export type UseQueryAnyReturn<Result> = Omit<
  * React hook to execute a PostgREST query and return a single item response.
  *
  * @param {PromiseLike<PostgrestSingleResponse<Result>>} query A promise that resolves to a PostgREST single item response.
- * @param {Omit<UseReactQueryOptions<PostgrestSingleResponse<Result>, PostgrestError>, 'queryKey' | 'queryFn'>} [config] The React Query options.
- * @returns {UseQuerySingleReturn<Result>} The hook result containing the single item response data.
+ * @param {Omit<UseReactQueryOptions<PostgrestSingleResponse<TransformedResult>, PostgrestError>, 'queryKey' | 'queryFn'>} [config] The React Query options.
+ * @returns {UseQuerySingleReturn<TransformedResult>} The hook result containing the single item response data.
  */
-function useQuery<Result>(
+function useQuery<Result, TransformedResult = Result>(
   query: PromiseLike<PostgrestSingleResponse<Result>>,
   config?: Omit<
-    UseReactQueryOptions<PostgrestSingleResponse<Result>, PostgrestError>,
+    UseReactQueryOptions<
+      PostgrestSingleResponse<TransformedResult>,
+      PostgrestError
+    >,
     'queryKey' | 'queryFn'
-  >,
-): UseQuerySingleReturn<Result>;
+  > & {
+    transformer?: (
+      data: PostgrestSingleResponse<Result>['data'],
+    ) => TransformedResult;
+  },
+): UseQuerySingleReturn<TransformedResult>;
 /**
  * React hook to execute a PostgREST query and return a maybe single item response.
  *
  * @param {PromiseLike<PostgrestMaybeSingleResponse<Result>>} query A promise that resolves to a PostgREST maybe single item response.
- * @param {Omit<UseReactQueryOptions<PostgrestMaybeSingleResponse<Result>, PostgrestError>, 'queryKey' | 'queryFn'>} [config] The React Query options.
- * @returns {UseQueryMaybeSingleReturn<Result>} The hook result containing the maybe single item response data.
+ * @param {Omit<UseReactQueryOptions<PostgrestMaybeSingleResponse<TransformedResult>, PostgrestError>, 'queryKey' | 'queryFn'>} [config] The React Query options.
+ * @returns {UseQueryMaybeSingleReturn<TransformedResult>} The hook result containing the maybe single item response data.
  */
-function useQuery<Result>(
+function useQuery<Result, TransformedResult = Result>(
   query: PromiseLike<PostgrestMaybeSingleResponse<Result>>,
   config?: Omit<
-    UseReactQueryOptions<PostgrestMaybeSingleResponse<Result>, PostgrestError>,
+    UseReactQueryOptions<
+      PostgrestMaybeSingleResponse<TransformedResult>,
+      PostgrestError
+    >,
     'queryKey' | 'queryFn'
-  >,
-): UseQueryMaybeSingleReturn<Result>;
+  > & {
+    transformer?: (
+      data: PostgrestMaybeSingleResponse<Result>['data'],
+    ) => TransformedResult;
+  },
+): UseQueryMaybeSingleReturn<TransformedResult>;
 /**
  * React hook to execute a PostgREST query.
  *
  * @template Result The expected response data type.
  * @param {PromiseLike<PostgrestResponse<Result>>} query A promise that resolves to a PostgREST response.
- * @param {Omit<UseReactQueryOptions<PostgrestResponse<Result>, PostgrestError>, 'queryKey' | 'queryFn'>} [config] The React Query options.
- * @returns {UseQueryReturn<Result>} The hook result containing the response data.
+ * @param {Omit<UseReactQueryOptions<PostgrestResponse<TransformedResult>, PostgrestError>, 'queryKey' | 'queryFn'>} [config] The React Query options.
+ * @returns {UseQueryReturn<TransformedResult>} The hook result containing the response data.
  */
-function useQuery<Result>(
+function useQuery<Result, TransformedResult = Result>(
   query: PromiseLike<PostgrestResponse<Result>>,
   config?: Omit<
-    UseReactQueryOptions<PostgrestResponse<Result>, PostgrestError>,
+    UseReactQueryOptions<PostgrestResponse<TransformedResult>, PostgrestError>,
     'queryKey' | 'queryFn'
-  >,
-): UseQueryReturn<Result>;
+  > & {
+    transformer?: (
+      data: PostgrestResponse<Result>['data'],
+    ) => TransformedResult;
+  },
+): UseQueryReturn<TransformedResult>;
 
 /**
  * React hook to execute a PostgREST query.
  *
  * @template Result The expected response data type.
  * @param {PromiseLike<AnyPostgrestResponse<Result>>} query A promise that resolves to a PostgREST response of any kind.
- * @param {Omit<UseReactQueryOptions<AnyPostgrestResponse<Result>, PostgrestError>, 'queryKey' | 'queryFn'>} [config] The React Query options.
- * @returns {UseQueryAnyReturn<Result>} The hook result containing the response data.
+ * @param {Omit<UseReactQueryOptions<AnyPostgrestResponse<TransformedResult>, PostgrestError>, 'queryKey' | 'queryFn'>} [config] The React Query options.
+ * @returns {UseQueryAnyReturn<TransformedResult>} The hook result containing the response data.
  */
-function useQuery<Result>(
+function useQuery<Result, TransformedResult = Result>(
   query: PromiseLike<AnyPostgrestResponse<Result>>,
   config?: Omit<
-    UseReactQueryOptions<AnyPostgrestResponse<Result>, PostgrestError>,
+    UseReactQueryOptions<
+      AnyPostgrestResponse<TransformedResult>,
+      PostgrestError
+    >,
     'queryKey' | 'queryFn'
-  >,
-): UseQueryAnyReturn<Result> {
+  > & {
+    transformer?: (
+      data: AnyPostgrestResponse<Result>['data'],
+    ) => TransformedResult;
+  },
+): UseQueryAnyReturn<TransformedResult> {
   const { data, ...rest } = useReactQuery<
-    AnyPostgrestResponse<Result>,
+    AnyPostgrestResponse<TransformedResult>,
     PostgrestError
-  >(buildQueryOpts<Result>(query, config));
+  >(buildQueryOpts<Result, TransformedResult>(query, config));
 
   return { data: data?.data, count: data?.count ?? null, ...rest };
 }