Tertiary trisomy is uncommon and may arise only when one of the derivatives is small and, in the abnormal individual with karyotype 47, exists as a supernumerary derivative chromosome (+der). We describe a case of 47, XY, +der(9)t(5;9) (q33.1;q13)mat. The patient (a 1-day-old male) presented with multiple congenital anomalies including microcephaly, wide fontanelles and sutures, microphthalmia, deep-set eyes, short palpebral fissures, bulbous nose, wide nasal bridge, high arched palate, low-set and posteriorly rotated ears, micrognathia, short neck, ptosis, patient ductus arteriosus, hypoplastic external genitalia, cryptorchidism, inguinal hernia, flexion contractures of joints, short stature, clenched hands, rocker-bottom feet, simian crease, distal mottling of the skin, nail hypoplasia, hypoplasia of bones and hydrocephalus. The supernumerary derivative chromosome resulted from a meiotic recombination of a maternal balanced translocation, t(5;9) (q33.1;q13), suggesting that 3:1 disjunction in the oocyte occurred.