diff --git a/app/code/Magento/QuoteGraphQl/Model/Cart/UpdateCartItem.php b/app/code/Magento/QuoteGraphQl/Model/Cart/UpdateCartItem.php
new file mode 100644
index 0000000000000..bc98eb93b55cc
--- /dev/null
+++ b/app/code/Magento/QuoteGraphQl/Model/Cart/UpdateCartItem.php
@@ -0,0 +1,98 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+namespace Magento\QuoteGraphQl\Model\Cart;
+
+use Magento\Framework\DataObject;
+use Magento\Framework\DataObjectFactory;
+use Magento\Framework\Exception\LocalizedException;
+use Magento\Framework\GraphQl\Exception\GraphQlInputException;
+use Magento\Quote\Model\Quote;
+
+/**
+ * Update cart item
+ *
+ */
+class UpdateCartItem
+{
+    /**
+     * @var DataObjectFactory
+     */
+    private $dataObjectFactory;
+
+    /**
+     * @param DataObjectFactory $dataObjectFactory
+     */
+    public function __construct(
+        DataObjectFactory $dataObjectFactory
+    ) {
+        $this->dataObjectFactory = $dataObjectFactory;
+    }
+
+    /**
+     * Update cart item
+     *
+     * @param Quote $cart
+     * @param int $cartItemId
+     * @param float $qty
+     * @param null $customizableOptionsData
+     * @return void
+     * @throws GraphQlInputException
+     */
+    public function execute(Quote $cart, int $cartItemId, float $qty, array $customizableOptionsData): void
+    {
+        $customizableOptions = [];
+        foreach ($customizableOptionsData as $customizableOption) {
+            $customizableOptions[$customizableOption['id']] = $customizableOption['value'];
+        }
+
+        try {
+            $result = $cart->updateItem(
+                $cartItemId,
+                $this->createBuyRequest($qty, $customizableOptions)
+            );
+        } catch (LocalizedException $e) {
+            throw new GraphQlInputException(
+                __(
+                    'Could not update cart item: %message',
+                    ['message' => $e->getMessage()]
+                )
+            );
+        }
+
+        if (is_string($result)) {
+            throw new GraphQlInputException(__(
+                'Could not update cart item: %message',
+                ['message' => $result]
+            ));
+        }
+
+        if ($result->getHasError()) {
+            throw new GraphQlInputException(__(
+                'Could not update cart item: %message',
+                ['message' => $result->getMessage()]
+            ));
+        }
+    }
+
+    /**
+     * Format GraphQl input data to a shape that buy request has
+     *
+     * @param float $qty
+     * @param array $customOptions
+     * @return DataObject
+     */
+    private function createBuyRequest(float $qty, array $customOptions): DataObject
+    {
+        return $this->dataObjectFactory->create([
+            'data' => [
+                'qty' => $qty,
+                'options' => $customOptions,
+            ],
+        ]);
+    }
+}
diff --git a/app/code/Magento/QuoteGraphQl/Model/Resolver/UpdateCartItems.php b/app/code/Magento/QuoteGraphQl/Model/Resolver/UpdateCartItems.php
index 78a07506556c0..ed1cb7a9dab50 100644
--- a/app/code/Magento/QuoteGraphQl/Model/Resolver/UpdateCartItems.php
+++ b/app/code/Magento/QuoteGraphQl/Model/Resolver/UpdateCartItems.php
@@ -15,14 +15,26 @@
 use Magento\Framework\GraphQl\Query\ResolverInterface;
 use Magento\Framework\GraphQl\Schema\Type\ResolveInfo;
 use Magento\Quote\Api\CartItemRepositoryInterface;
+use Magento\Quote\Api\CartRepositoryInterface;
 use Magento\Quote\Model\Quote;
 use Magento\QuoteGraphQl\Model\Cart\GetCartForUser;
+use Magento\QuoteGraphQl\Model\Cart\UpdateCartItem;
 
 /**
  * @inheritdoc
  */
 class UpdateCartItems implements ResolverInterface
 {
+    /**
+     * @var CartRepositoryInterface
+     */
+    private $quoteRepository;
+
+    /**
+     * @var UpdateCartItem
+     */
+    private $updateCartItem;
+
     /**
      * @var GetCartForUser
      */
@@ -36,13 +48,19 @@ class UpdateCartItems implements ResolverInterface
     /**
      * @param GetCartForUser $getCartForUser
      * @param CartItemRepositoryInterface $cartItemRepository
+     * @param UpdateCartItem $updateCartItem
+     * @param CartRepositoryInterface $quoteRepository
      */
     public function __construct(
         GetCartForUser $getCartForUser,
-        CartItemRepositoryInterface $cartItemRepository
+        CartItemRepositoryInterface $cartItemRepository,
+        UpdateCartItem $updateCartItem,
+        CartRepositoryInterface $quoteRepository
     ) {
         $this->getCartForUser = $getCartForUser;
         $this->cartItemRepository = $cartItemRepository;
+        $this->updateCartItem = $updateCartItem;
+        $this->quoteRepository = $quoteRepository;
     }
 
     /**
@@ -93,26 +111,47 @@ private function processCartItems(Quote $cart, array $items): void
             if (!isset($item['cart_item_id']) || empty($item['cart_item_id'])) {
                 throw new GraphQlInputException(__('Required parameter "cart_item_id" for "cart_items" is missing.'));
             }
-            $itemId = $item['cart_item_id'];
+            $itemId = (int)$item['cart_item_id'];
 
             if (!isset($item['quantity'])) {
                 throw new GraphQlInputException(__('Required parameter "quantity" for "cart_items" is missing.'));
             }
             $qty = (float)$item['quantity'];
 
-            $cartItem = $cart->getItemById($itemId);
-            if ($cartItem === false) {
-                throw new GraphQlNoSuchEntityException(
-                    __('Could not find cart item with id: %1.', $item['cart_item_id'])
-                );
-            }
-
             if ($qty <= 0.0) {
                 $this->cartItemRepository->deleteById((int)$cart->getId(), $itemId);
             } else {
-                $cartItem->setQty($qty);
-                $this->cartItemRepository->save($cartItem);
+                $customizableOptions = $item['customizable_options'] ?? null;
+
+                if ($customizableOptions === null) { // Update only item's qty
+                    $this->updateItemQty($itemId, $cart, $qty);
+                } else { // Update customizable options (and QTY if changed)
+                    $this->updateCartItem->execute($cart, $itemId, $qty, $customizableOptions);
+                    $this->quoteRepository->save($cart);
+                }
             }
         }
     }
+
+    /**
+     * Updates item qty for the specified cart
+     *
+     * @param int $itemId
+     * @param Quote $cart
+     * @param float $qty
+     * @throws GraphQlNoSuchEntityException
+     * @throws NoSuchEntityException
+     * @throws GraphQlNoSuchEntityException
+     */
+    private function updateItemQty(int $itemId, Quote $cart, float $qty)
+    {
+        $cartItem = $cart->getItemById($itemId);
+        if ($cartItem === false) {
+            throw new GraphQlNoSuchEntityException(
+                __('Could not find cart item with id: %1.', $itemId)
+            );
+        }
+        $cartItem->setQty($qty);
+        $this->cartItemRepository->save($cartItem);
+    }
 }
diff --git a/app/code/Magento/QuoteGraphQl/etc/schema.graphqls b/app/code/Magento/QuoteGraphQl/etc/schema.graphqls
index a9784e97c8952..afbb8ceb03b39 100644
--- a/app/code/Magento/QuoteGraphQl/etc/schema.graphqls
+++ b/app/code/Magento/QuoteGraphQl/etc/schema.graphqls
@@ -67,7 +67,8 @@ input UpdateCartItemsInput {
 
 input CartItemQuantityInput {
     cart_item_id: Int!
-    quantity: Float!
+    quantity: Float
+    customizable_options: [CustomizableOptionInput!]
 }
 
 input RemoveItemFromCartInput {