diff --git a/tests/posix/eventfd/src/ioctl.c b/tests/posix/eventfd/src/ioctl.c
new file mode 100644
index 0000000..28c2ce5
--- /dev/null
+++ b/tests/posix/eventfd/src/ioctl.c
@@ -0,0 +1,90 @@
+/*
+ * Copyright (c) 2024 Celina Sophie Kalus
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include "_main.h"
+#include <zephyr/posix/sys/ioctl.h>
+
+#define EFD_IN_USE_INTERNAL 0x1
+
+ZTEST_F(eventfd, test_set_flags)
+{
+	eventfd_t val;
+	int ret;
+	int flags;
+	short event;
+
+	/* Get current flags; Expect blocking, non-semaphore. */
+	flags = ioctl(fixture->fd, F_GETFL, 0);
+	zassert_equal(flags, 0, "flags == %d", flags);
+
+	event = POLLIN;
+	ret = is_blocked(fixture->fd, &event);
+	zassert_equal(ret, 1, "eventfd read not blocked");
+
+	/* Try writing and reading. Should not fail. */
+	ret = eventfd_write(fixture->fd, 3);
+	zassert_ok(ret);
+
+	ret = eventfd_read(fixture->fd, &val);
+	zassert_ok(ret);
+	zassert_equal(val, 3, "val == %d", val);
+
+
+	/* Set nonblocking without reopening. */
+	ret = ioctl(fixture->fd, F_SETFL, O_NONBLOCK);
+	zassert_ok(ret);
+
+	flags = ioctl(fixture->fd, F_GETFL, 0);
+	zassert_equal(flags, O_NONBLOCK, "flags == %d", flags);
+
+	event = POLLOUT;
+	ret = is_blocked(fixture->fd, &event);
+	zassert_equal(ret, 0, "eventfd write blocked");
+
+
+	/* Try writing and reading again. */
+	ret = eventfd_write(fixture->fd, 19);
+	zassert_ok(ret);
+
+	ret = eventfd_read(fixture->fd, &val);
+	zassert_ok(ret);
+	zassert_equal(val, 19, "val == %d", val);
+
+
+	/* Set back to blocking. */
+	ret = ioctl(fixture->fd, F_SETFL, 0);
+	zassert_ok(ret);
+
+	flags = ioctl(fixture->fd, F_GETFL, 0);
+	zassert_equal(flags, 0, "flags == %d", flags);
+
+	event = POLLIN;
+	ret = is_blocked(fixture->fd, &event);
+	zassert_equal(ret, 1, "eventfd read not blocked");
+
+
+	/* Try writing and reading again. */
+	ret = eventfd_write(fixture->fd, 10);
+	zassert_ok(ret);
+
+	ret = eventfd_read(fixture->fd, &val);
+	zassert_ok(ret);
+	zassert_equal(val, 10, "val == %d", val);
+
+
+	/* Test setting internal in-use-flag. Should fail. */
+	ret = ioctl(fixture->fd, F_SETFL, EFD_IN_USE_INTERNAL);
+	zassert_not_ok(ret);
+
+
+	/* File descriptor should still be valid and working. */
+	ret = eventfd_write(fixture->fd, 97);
+	zassert_ok(ret);
+
+	ret = eventfd_read(fixture->fd, &val);
+	zassert_ok(ret);
+	zassert_equal(val, 97, "val == %d", val);
+}