diff --git a/modules/rostests/apitests/ntdll/CMakeLists.txt b/modules/rostests/apitests/ntdll/CMakeLists.txt
index a98bce7247b..5c60d004f1c 100644
--- a/modules/rostests/apitests/ntdll/CMakeLists.txt
+++ b/modules/rostests/apitests/ntdll/CMakeLists.txt
@@ -62,6 +62,7 @@ list(APPEND SOURCE
     NtDuplicateToken.c
     NtFilterToken.c
     NtFreeVirtualMemory.c
+    NtGetCurrentProcessorNumberEx.c
     NtImpersonateAnonymousToken.c
     NtLoadUnloadKey.c
     NtMapViewOfSection.c
diff --git a/modules/rostests/apitests/ntdll/NtGetCurrentProcessorNumberEx.c b/modules/rostests/apitests/ntdll/NtGetCurrentProcessorNumberEx.c
new file mode 100644
index 00000000000..c7da6f88152
--- /dev/null
+++ b/modules/rostests/apitests/ntdll/NtGetCurrentProcessorNumberEx.c
@@ -0,0 +1,44 @@
+/*
+ * PROJECT:     ReactOS api tests
+ * LICENSE:     MIT (https://spdx.org/licenses/MIT)
+ * PURPOSE:     Tests for NtGetCurrentProcessorNumberEx
+ * COPYRIGHT:   Copyright 2025 Timo Kreuzer <timo.kreuzer@reactos.org>
+ */
+
+#include "precomp.h"
+#include <winnls.h>
+
+typedef
+NTSTATUS
+NTAPI
+FN_NtGetCurrentProcessorNumberEx(
+    _Out_ PPROCESSOR_NUMBER);
+
+FN_NtGetCurrentProcessorNumberEx* pNtGetCurrentProcessorNumberEx;
+
+START_TEST(NtGetCurrentProcessorNumberEx)
+{
+    PROCESSOR_NUMBER ProcessorNumber;
+    NTSTATUS Status;
+
+    HINSTANCE hinstNtdll = GetModuleHandleA("ntdll.dll");
+    pNtGetCurrentProcessorNumberEx = (FN_NtGetCurrentProcessorNumberEx*)GetProcAddress(hinstNtdll, "NtGetCurrentProcessorNumberEx");
+    if (!pNtGetCurrentProcessorNumberEx)
+    {
+        skip("NtGetCurrentProcessorNumberEx is not available\n");
+        return;
+    }
+
+    memset(&ProcessorNumber, 0xAA, sizeof(ProcessorNumber));
+    Status = pNtGetCurrentProcessorNumberEx(&ProcessorNumber);
+    ok_eq_hex(Status, STATUS_SUCCESS);
+    ok(ProcessorNumber.Group < 64, "Processor group is out of range");
+    ok(ProcessorNumber.Number < 64, "Processor number is out of range");
+    ok(ProcessorNumber.Reserved == 0, "Reserved field is not zero");
+
+    Status = pNtGetCurrentProcessorNumberEx(NULL);
+    ok_eq_hex(Status, STATUS_ACCESS_VIOLATION);
+
+    Status = pNtGetCurrentProcessorNumberEx((PVOID)(ULONG_PTR)0xDEADDEADDEADDEADull);
+    ok_eq_hex(Status, STATUS_ACCESS_VIOLATION);
+}