Fetus-in-fetu is a rare congenital malformation in which a vertebra fetus is enclosed within the abdomen of a normally developing fetus. Magnetic resonance imaging (MRI) appears to be an ideal tool for demonstrating the wide range of tissue within such lesions, but there are only a few reports of the use of MRI in the identification of this anomaly. We present a case of fetus-in-fetu in which the MRI findings were diagnostic clues of this unusual entity.