Double uterus is a rare form of uterine malformation resulting from an incomplete fusion of the Müllerian ducts. Thanks to availability of numerous imaging tests its diagnostics in general does not present clinical problems. It is assumed that in the diagnosis of double uterus the following examinations can be helpful: transvaginal ultrasonography, sonohysterography, hysterosalpingography, magnetic resonance imaging, hysteroscopy, and 3D Ultrasound. The presented case report has proved that in certain clinical states the diagnosis of double uterus can be difficult, and the modern imaging techniques are only additional examinations, which can help to make a diagnosis but cannot establish it on their own.