Polydactyly is a congenital anomaly of very low incidence in horses. A 6-week-old filly with polydactyly in all four limbs was admitted for a clinical and radiological examination. This examination showed the presence of a supernumerary digit for the digit II with respect to the metacarpal bone and the first and second phalanges in both forelimbs. In both hindlimbs a supernumerary digit was observed to originate at the level of the phalangic metatarsal joint. Both digits were the same size, and formed by three phalanges and were articulated with the metatarsi bone III. First phalanges of both digits were partially fused proximally. In the left hindlimb had osteomelitis, and a fracture in the lateral digit. Due to bone compromise and pain, euthanasia was performed. Cytogenic analysis was not performed. According to the used classification polydactyly described in the forelimbs corresponds to atavistic, and described in the hindlimbs to teratogenic form. As far as we know, this is the first case of polydactyly in all four limbs described in South America and the first in the world in the last 55 years.