diff --git a/src/lib/actions/order-item.test.ts b/src/lib/actions/order-item.test.ts
index 0bab7c1..808dcbd 100644
--- a/src/lib/actions/order-item.test.ts
+++ b/src/lib/actions/order-item.test.ts
@@ -1,21 +1,25 @@
-import { createOrderItem } from '@/lib/actions/order-item';
+import { createOrderItem, editOrderItem } from '@/lib/actions/order-item';
 import { fakeOrderItem } from '@/lib/fakes/order-item';
 import { prismaMock } from '../../../test-setup/prisma-mock.setup';
 import { fakeBook } from '@/lib/fakes/book';
 import { fakeOrder } from '@/lib/fakes/order';
 import { computeTax } from '@/lib/money';
-import { ProductType } from '@prisma/client';
+import { Order, ProductType } from '@prisma/client';
 
 describe('order item actions', () => {
   const order1 = fakeOrder();
   const orderItem1 = fakeOrderItem();
+  const orderItem2 = fakeOrderItem();
   const book1 = fakeBook();
 
   describe('createOrderItem', () => {
     it('should create order item', async () => {
       prismaMock.$transaction.mockImplementation((cb) => cb(prismaMock));
       prismaMock.book.findUniqueOrThrow.mockResolvedValue(book1);
-      prismaMock.order.findUniqueOrThrow.mockResolvedValue(order1);
+      prismaMock.order.findUniqueOrThrow.mockResolvedValue({
+        ...order1,
+        orderItems: [orderItem1, orderItem2],
+      } as Order);
       prismaMock.order.update.mockResolvedValue(order1);
       orderItem1.orderId = order1.id;
       orderItem1.bookId = book1.id;
@@ -42,7 +46,7 @@ describe('order item actions', () => {
       });
 
       const subTotalInCents =
-        order1.subTotalInCents + orderItem1.totalPriceInCents;
+        orderItem1.totalPriceInCents + orderItem2.totalPriceInCents;
       const taxInCents = computeTax(subTotalInCents);
       const totalInCents = subTotalInCents + taxInCents;
       expect(prismaMock.order.update).toHaveBeenCalledWith({
@@ -69,4 +73,56 @@ describe('order item actions', () => {
       );
     });
   });
+
+  describe('editOrderItem', () => {
+    it('should edit an order item', async () => {
+      prismaMock.$transaction.mockImplementation((cb) => cb(prismaMock));
+      prismaMock.order.findUniqueOrThrow.mockResolvedValue({
+        ...order1,
+        orderItems: [
+          orderItem2,
+          {
+            ...orderItem1,
+            productPriceInCents: 10,
+            quantity: 2,
+            totalPriceInCents: 20,
+          },
+        ],
+      } as Order);
+      orderItem1.orderId = order1.id;
+      prismaMock.orderItem.update.mockResolvedValue(orderItem1);
+
+      const result = await editOrderItem({
+        orderItemId: order1.id,
+        orderItemUpdate: {
+          productPriceInCents: 10,
+          quantity: 2,
+          totalPriceInCents: 20,
+        },
+      });
+
+      expect(prismaMock.orderItem.update).toHaveBeenCalledWith({
+        data: {
+          productPriceInCents: 10,
+          quantity: 2,
+          totalPriceInCents: 20,
+        },
+        where: { id: order1.id },
+      });
+
+      const subTotalInCents = 20 + orderItem2.totalPriceInCents;
+      const taxInCents = computeTax(subTotalInCents);
+      const totalInCents = subTotalInCents + taxInCents;
+      expect(prismaMock.order.update).toHaveBeenCalledWith({
+        data: {
+          subTotalInCents,
+          taxInCents,
+          totalInCents,
+        },
+        where: { id: order1.id },
+      });
+
+      expect(result).toEqual(orderItem1);
+    });
+  });
 });
diff --git a/src/lib/actions/order-item.ts b/src/lib/actions/order-item.ts
index 33877b5..7abdf68 100644
--- a/src/lib/actions/order-item.ts
+++ b/src/lib/actions/order-item.ts
@@ -4,6 +4,7 @@ import { recomputeOrderTotals } from '@/lib/actions/order';
 import logger from '@/lib/logger';
 import prisma from '@/lib/prisma';
 import OrderItemCreateInput from '@/types/OrderItemCreateInput';
+import OrderItemUpdateInput from '@/types/OrderItemUpdateInput';
 import { OrderItem, Prisma, ProductType } from '@prisma/client';
 
 export async function createOrderItem(
@@ -41,7 +42,7 @@ export async function createOrderItem(
 
       logger.trace('created order item in DB: %j', createdOrderItem);
 
-      await recomputeOrderTotals({ orderItem: createdOrderItem, tx });
+      await recomputeOrderTotals({ orderId: createdOrderItem.orderId, tx });
 
       return createdOrderItem;
     },
@@ -50,3 +51,34 @@ export async function createOrderItem(
     },
   );
 }
+
+export async function editOrderItem({
+  orderItemId,
+  orderItemUpdate,
+}: {
+  orderItemId: OrderItem['id'];
+  orderItemUpdate: OrderItemUpdateInput;
+}): Promise<OrderItem> {
+  return prisma.$transaction(
+    async (tx) => {
+      const { productPriceInCents, quantity, totalPriceInCents } =
+        orderItemUpdate;
+
+      const orderItem = await tx.orderItem.update({
+        data: {
+          productPriceInCents,
+          quantity,
+          totalPriceInCents,
+        },
+        where: { id: orderItemId },
+      });
+
+      await recomputeOrderTotals({ orderId: orderItem.orderId, tx });
+
+      return orderItem;
+    },
+    {
+      isolationLevel: Prisma.TransactionIsolationLevel.Serializable,
+    },
+  );
+}
diff --git a/src/lib/actions/order.ts b/src/lib/actions/order.ts
index 131d23f..f2e0d75 100644
--- a/src/lib/actions/order.ts
+++ b/src/lib/actions/order.ts
@@ -14,13 +14,7 @@ import OrderHydrated from '@/types/OrderHydrated';
 import OrderWithItemsHydrated from '@/types/OrderWithItemsHydrated';
 import PageInfo from '@/types/PageInfo';
 import PaginationQuery from '@/types/PaginationQuery';
-import {
-  Order,
-  OrderItem,
-  OrderState,
-  Prisma,
-  ProductType,
-} from '@prisma/client';
+import { Order, OrderState, Prisma, ProductType } from '@prisma/client';
 import { format } from 'date-fns';
 
 export async function createOrder(): Promise<OrderWithItemsHydrated> {
@@ -50,19 +44,23 @@ export async function createOrder(): Promise<OrderWithItemsHydrated> {
 }
 
 export async function recomputeOrderTotals({
-  orderItem,
+  orderId,
   tx,
 }: {
-  orderItem: OrderItem;
+  orderId: Order['id'];
   tx: Prisma.TransactionClient;
 }): Promise<void> {
-  const { orderId } = orderItem;
-
   const order = await tx.order.findUniqueOrThrow({
+    include: {
+      orderItems: true,
+    },
     where: { id: orderId },
   });
 
-  const subTotalInCents = order.subTotalInCents + orderItem.totalPriceInCents;
+  const subTotalInCents = order.orderItems.reduce(
+    (total, item) => total + item.totalPriceInCents,
+    0,
+  );
   const taxInCents = computeTax(subTotalInCents);
   const totalInCents = subTotalInCents + taxInCents;
 
diff --git a/src/types/OrderItemUpdateInput.ts b/src/types/OrderItemUpdateInput.ts
new file mode 100644
index 0000000..a4b835e
--- /dev/null
+++ b/src/types/OrderItemUpdateInput.ts
@@ -0,0 +1,7 @@
+import { OrderItem } from '@prisma/client';
+
+type OrderItemUpdateInput = Pick<
+  OrderItem,
+  'productPriceInCents' | 'quantity' | 'totalPriceInCents'
+>;
+export default OrderItemUpdateInput;