Complete diphallia was detected in a six-month-old Poodle cross dog. Duplication of the urinary bladder, right renal hypoplasia, bifurcation of the descending colon and bilateral cryptorchidism were also present. The left urethra was patent, and emptied the left urinary bladder; the right urethra ended blindly at a point 2.5 cm from the tip of the right penis. The left urinary bladder was joined medially to a right urinary bladder with no interbladder communication; however, the right bladder opened caudally into a blind sac which drained into the left prostatic urethra. Pyelonephritis of the left kidney was present, and was suspected to be due to ascending bacterial infection of the right urinary bladder and the right segment of the bifurcated descending colon, which terminated at the apex of the right urinary bladder. Diphallia and associated urogenital anomalies are reviewed.