diff --git a/modules/rostests/apitests/ntdll/CMakeLists.txt b/modules/rostests/apitests/ntdll/CMakeLists.txt
index ef5f6a61302..86613855448 100644
--- a/modules/rostests/apitests/ntdll/CMakeLists.txt
+++ b/modules/rostests/apitests/ntdll/CMakeLists.txt
@@ -10,6 +10,7 @@ list(APPEND SOURCE
     load_notifications.c
     locale.c
     NtAcceptConnectPort.c
+    NtAdjustPrivilegesToken.c
     NtAllocateVirtualMemory.c
     NtApphelpCacheControl.c
     NtCompareTokens.c
diff --git a/modules/rostests/apitests/ntdll/NtAdjustPrivilegesToken.c b/modules/rostests/apitests/ntdll/NtAdjustPrivilegesToken.c
new file mode 100644
index 00000000000..363609ad2f2
--- /dev/null
+++ b/modules/rostests/apitests/ntdll/NtAdjustPrivilegesToken.c
@@ -0,0 +1,87 @@
+/*
+ * PROJECT:         ReactOS API tests
+ * LICENSE:         GPL-2.0-or-later (https://spdx.org/licenses/GPL-2.0-or-later)
+ * PURPOSE:         Tests for the NtAdjustPrivilegesToken API
+ * COPYRIGHT:       Copyright 2021 George Bișoc <george.bisoc@reactos.org>
+ */
+
+#include "precomp.h"
+
+static
+BOOL
+IsPrivilegeEnabled(
+    _In_ HANDLE TokenHandle,
+    _In_ ULONG Privilege)
+{
+    PRIVILEGE_SET PrivSet;
+    BOOL Result, Success;
+    LUID Priv;
+
+    ConvertPrivLongToLuid(Privilege, &Priv);
+
+    PrivSet.PrivilegeCount = 1;
+    PrivSet.Control = PRIVILEGE_SET_ALL_NECESSARY;
+    PrivSet.Privilege[0].Luid = Priv;
+    PrivSet.Privilege[0].Attributes = 0;
+
+    Success = PrivilegeCheck(TokenHandle, &PrivSet, &Result);
+    if (!Success)
+    {
+        skip("Failed to check the privilege (error code: %lu)\n", GetLastError());
+        return FALSE;
+    }
+
+    return Result;
+}
+
+static
+VOID
+AdjustEnableDefaultPriv(VOID)
+{
+    NTSTATUS Status;
+    HANDLE Token;
+    TOKEN_PRIVILEGES Priv;
+    BOOL Success, IsEnabled;
+    LUID PrivLuid;
+
+    Success = OpenProcessToken(GetCurrentProcess(),
+                               TOKEN_READ | TOKEN_ADJUST_PRIVILEGES,
+                               &Token);
+    if (!Success)
+    {
+        skip("OpenProcessToken() has failed to get the process' token (error code: %lu)!\n", GetLastError());
+        return;
+    }
+
+    Success = LookupPrivilegeValueW(NULL, L"SeImpersonatePrivilege", &PrivLuid);
+    if (!Success)
+    {
+        skip("LookupPrivilegeValueW() has failed to locate the privilege value (error code: %lu)!\n", GetLastError());
+        return;
+    }
+
+    Priv.PrivilegeCount = 1;
+    Priv.Privileges[0].Luid = PrivLuid;
+    Priv.Privileges[0].Attributes = 0;
+
+    IsEnabled = IsPrivilegeEnabled(Token, SE_IMPERSONATE_PRIVILEGE);
+    trace("The privilege is %s!\n", IsEnabled ? "enabled" : "disabled");
+
+    Status = NtAdjustPrivilegesToken(Token,
+                                     FALSE,
+                                     &Priv,
+                                     0,
+                                     NULL,
+                                     NULL);
+    ok_hex(Status, STATUS_SUCCESS);
+
+    IsEnabled = IsPrivilegeEnabled(Token, SE_IMPERSONATE_PRIVILEGE);
+    trace("The privilege is %s!\n", IsEnabled ? "enabled" : "disabled");
+
+    CloseHandle(Token);
+}
+
+START_TEST(NtAdjustPrivilegesToken)
+{
+    AdjustEnableDefaultPriv();
+}
diff --git a/modules/rostests/apitests/ntdll/precomp.h b/modules/rostests/apitests/ntdll/precomp.h
index 4871076a873..6b8ea6e1b0a 100644
--- a/modules/rostests/apitests/ntdll/precomp.h
+++ b/modules/rostests/apitests/ntdll/precomp.h
@@ -41,4 +41,12 @@ SetupLocale(
     _In_ ULONG OemCode,
     _In_ ULONG Unicode);
 
+#define ConvertPrivLongToLuid(PrivilegeVal, ConvertedPrivLuid) \
+do {                                                           \
+    LUID Luid;                                                 \
+    Luid.LowPart = PrivilegeVal;                               \
+    Luid.HighPart = 0;                                         \
+    *ConvertedPrivLuid = Luid;                                 \
+} while (0)
+
 #endif /* _NTDLL_APITEST_PRECOMP_H_ */
diff --git a/modules/rostests/apitests/ntdll/testlist.c b/modules/rostests/apitests/ntdll/testlist.c
index 5a56ec6e987..49458f43f09 100644
--- a/modules/rostests/apitests/ntdll/testlist.c
+++ b/modules/rostests/apitests/ntdll/testlist.c
@@ -6,6 +6,7 @@
 extern void func_LdrEnumResources(void);
 extern void func_load_notifications(void);
 extern void func_NtAcceptConnectPort(void);
+extern void func_NtAdjustPrivilegesToken(void);
 extern void func_NtAllocateVirtualMemory(void);
 extern void func_NtApphelpCacheControl(void);
 extern void func_NtCompareTokens(void);
@@ -90,6 +91,7 @@ const struct test winetest_testlist[] =
     { "LdrEnumResources",               func_LdrEnumResources },
     { "load_notifications",             func_load_notifications },
     { "NtAcceptConnectPort",            func_NtAcceptConnectPort },
+    { "NtAdjustPrivilegesToken",        func_NtAdjustPrivilegesToken },
     { "NtAllocateVirtualMemory",        func_NtAllocateVirtualMemory },
     { "NtApphelpCacheControl",          func_NtApphelpCacheControl },
     { "NtCompareTokens",                func_NtCompareTokens },