diff --git a/UPGRADE-14.0.md b/UPGRADE-14.0.md
index 21bf06c7c2c..4b9d958f5d1 100644
--- a/UPGRADE-14.0.md
+++ b/UPGRADE-14.0.md
@@ -1501,6 +1501,11 @@ Follow the instructions in relevant sections, e.g. `shopsys/coding-standards` or
     -   see #project-base-diff to update your project
 
 -   take promo code into account in priceByTransportQuery and priceByPaymentQuery ([#3118](https://github.com/shopsys/shopsys/pull/3118))
+
+    -   see #project-base-diff to update your project
+
+-   addProductToListMutation: ensure new product list is created with non-conflicting uuid ([#3126](https://github.com/shopsys/shopsys/pull/3126))
+    -   add new tests to `ProductListLoggedCustomerTest` and `ProductListNotLoggedCustomerTest` classes
     -   see #project-base-diff to update your project
 
 ### Storefront
diff --git a/packages/framework/src/Model/Product/List/ProductListFacade.php b/packages/framework/src/Model/Product/List/ProductListFacade.php
index cb2e8108b5a..f3ab98d3f00 100644
--- a/packages/framework/src/Model/Product/List/ProductListFacade.php
+++ b/packages/framework/src/Model/Product/List/ProductListFacade.php
@@ -108,6 +108,15 @@ public function findAnonymousProductList(
         return $this->productListRepository->findAnonymousProductList($uuid, $productListType);
     }
 
+    /**
+     * @param string $uuid
+     * @return bool
+     */
+    public function existsProductListWithUuid(string $uuid): bool
+    {
+        return $this->productListRepository->existsProductListWithUuid($uuid);
+    }
+
     /**
      * @param \Shopsys\FrameworkBundle\Model\Product\List\ProductList $productList
      * @param \Shopsys\FrameworkBundle\Model\Product\Product $product
diff --git a/packages/framework/src/Model/Product/List/ProductListRepository.php b/packages/framework/src/Model/Product/List/ProductListRepository.php
index bc9553396a2..0afaa035752 100644
--- a/packages/framework/src/Model/Product/List/ProductListRepository.php
+++ b/packages/framework/src/Model/Product/List/ProductListRepository.php
@@ -119,4 +119,13 @@ protected function getRepository(): EntityRepository
     {
         return $this->entityManager->getRepository(ProductList::class);
     }
+
+    /**
+     * @param string $uuid
+     * @return bool
+     */
+    public function existsProductListWithUuid(string $uuid): bool
+    {
+        return $this->getRepository()->count(['uuid' => $uuid]) > 0;
+    }
 }
diff --git a/packages/frontend-api/src/Model/Mutation/ProductList/ProductListMutation.php b/packages/frontend-api/src/Model/Mutation/ProductList/ProductListMutation.php
index b718a16fdfe..f516ad4f629 100644
--- a/packages/frontend-api/src/Model/Mutation/ProductList/ProductListMutation.php
+++ b/packages/frontend-api/src/Model/Mutation/ProductList/ProductListMutation.php
@@ -5,6 +5,7 @@
 namespace Shopsys\FrontendApiBundle\Model\Mutation\ProductList;
 
 use Overblog\GraphQLBundle\Definition\Argument;
+use Ramsey\Uuid\Uuid;
 use Shopsys\FrameworkBundle\Model\Customer\User\CurrentCustomerUser;
 use Shopsys\FrameworkBundle\Model\Product\Exception\ProductNotFoundException;
 use Shopsys\FrameworkBundle\Model\Product\List\Exception\ProductAlreadyInListException;
@@ -60,6 +61,10 @@ public function addProductToListMutation(Argument $argument): ProductList
         }
 
         if ($productList === null) {
+            if ($productListUuid !== null && $this->productListFacade->existsProductListWithUuid($productListUuid)) {
+                $productListUuid = Uuid::uuid4()->toString();
+            }
+
             $productListData = $this->productListDataFactory->create($productListType, $customerUser, $productListUuid);
             $productList = $this->productListFacade->create($productListData);
         }
diff --git a/project-base/app/tests/FrontendApiBundle/Functional/Product/ProductList/ProductListLoggedCustomerTest.php b/project-base/app/tests/FrontendApiBundle/Functional/Product/ProductList/ProductListLoggedCustomerTest.php
index 8f60b355de6..2121d451b0d 100644
--- a/project-base/app/tests/FrontendApiBundle/Functional/Product/ProductList/ProductListLoggedCustomerTest.php
+++ b/project-base/app/tests/FrontendApiBundle/Functional/Product/ProductList/ProductListLoggedCustomerTest.php
@@ -150,6 +150,28 @@ public function testAddProductCreatesNewListWhenNewUuidIsProvided(string $produc
         $this->assertSame([$productToAddId], array_column($data['products'], 'id'));
     }
 
+    /**
+     * @dataProvider \Tests\FrontendApiBundle\Functional\Product\ProductList\ProductListTypesDataProvider::getProductListTypes
+     * @param string $productListType
+     */
+    public function testAddProductCreatesNewListWithNewUuidWhenUuidOfAnonymousListIsProvided(
+        string $productListType,
+    ): void {
+        $anonymousProductListUuid = $this->getAnonymousProductListUuid($productListType);
+        $productToAddId = 69;
+        $productToAdd = $this->getReference(ProductDataFixture::PRODUCT_PREFIX . $productToAddId);
+        $response = $this->getResponseContentForGql(__DIR__ . '/graphql/AddProductToListMutation.graphql', [
+            'productListUuid' => $anonymousProductListUuid,
+            'productUuid' => $productToAdd->getUuid(),
+            'type' => $productListType,
+        ]);
+        $data = $this->getResponseDataForGraphQlType($response, 'AddProductToList');
+
+        $this->assertNotSame($anonymousProductListUuid, $data['uuid']);
+        $this->assertSame($productListType, $data['type']);
+        $this->assertSame([$productToAddId], array_column($data['products'], 'id'));
+    }
+
     /**
      * @dataProvider productListDataProvider
      * @param string $productListType
@@ -242,4 +264,17 @@ public function productListDataProvider(): Iterator
             'expectedProductIds' => [1],
         ];
     }
+
+    /**
+     * @param string $productListType
+     * @return string
+     */
+    private function getAnonymousProductListUuid(string $productListType): string
+    {
+        return match ($productListType) {
+            ProductListTypeEnum::COMPARISON => ProductListDataFixture::PRODUCT_LIST_COMPARISON_NOT_LOGGED_CUSTOMER_UUID,
+            ProductListTypeEnum::WISHLIST => ProductListDataFixture::PRODUCT_LIST_WISHLIST_NOT_LOGGED_CUSTOMER_UUID,
+            default => throw new UnknownProductListTypeException($productListType),
+        };
+    }
 }
diff --git a/project-base/app/tests/FrontendApiBundle/Functional/Product/ProductList/ProductListNotLoggedCustomerTest.php b/project-base/app/tests/FrontendApiBundle/Functional/Product/ProductList/ProductListNotLoggedCustomerTest.php
index fc262aafab4..be3f81d1564 100644
--- a/project-base/app/tests/FrontendApiBundle/Functional/Product/ProductList/ProductListNotLoggedCustomerTest.php
+++ b/project-base/app/tests/FrontendApiBundle/Functional/Product/ProductList/ProductListNotLoggedCustomerTest.php
@@ -166,6 +166,28 @@ public function testAddProductCreatesNewListWhenNewUuidIsProvided(string $produc
         $this->assertSame([$productToAddId], array_column($data['products'], 'id'));
     }
 
+    /**
+     * @dataProvider \Tests\FrontendApiBundle\Functional\Product\ProductList\ProductListTypesDataProvider::getProductListTypes
+     * @param string $productListType
+     */
+    public function testAddProductCreatesNewListWithNewUuidWhenUuidOfCustomerUserListIsProvided(
+        string $productListType,
+    ): void {
+        $customerUserProductListUuid = $this->getCustomerUserProductListUuid($productListType);
+        $productToAddId = 69;
+        $productToAdd = $this->getReference(ProductDataFixture::PRODUCT_PREFIX . $productToAddId);
+        $response = $this->getResponseContentForGql(__DIR__ . '/graphql/AddProductToListMutation.graphql', [
+            'productListUuid' => $customerUserProductListUuid,
+            'productUuid' => $productToAdd->getUuid(),
+            'type' => $productListType,
+        ]);
+        $data = $this->getResponseDataForGraphQlType($response, 'AddProductToList');
+
+        $this->assertNotSame($customerUserProductListUuid, $data['uuid']);
+        $this->assertSame($productListType, $data['type']);
+        $this->assertSame([$productToAddId], array_column($data['products'], 'id'));
+    }
+
     /**
      * @dataProvider \Tests\FrontendApiBundle\Functional\Product\ProductList\ProductListTypesDataProvider::getProductListTypes
      * @param string $productListType
@@ -471,4 +493,17 @@ private function assertOriginalAnonymousListsDoNotExist(): void
         $this->assertTrue($originalAnonymousWishlist === null, 'Original anonymous wishlist should not exist anymore');
         $this->assertTrue($originalAnonymousComparison === null, 'Original anonymous comparison should not exist anymore');
     }
+
+    /**
+     * @param string $productListType
+     * @return string
+     */
+    private function getCustomerUserProductListUuid(string $productListType): string
+    {
+        return match ($productListType) {
+            ProductListTypeEnum::COMPARISON => ProductListDataFixture::PRODUCT_LIST_COMPARISON_LOGGED_CUSTOMER_UUID,
+            ProductListTypeEnum::WISHLIST => ProductListDataFixture::PRODUCT_LIST_WISHLIST_LOGGED_CUSTOMER_UUID,
+            default => throw new UnknownProductListTypeException($productListType),
+        };
+    }
 }