This study reports a case of parasitism by the giant kidney worm, Dioctophyme renale (Goeze, 1782), in the abdominal cavity of a domestic cat from Brazil. A female adult cat presenting prostration, dehydration, physical debility, pronounced jaundice and ascitis, was taken to the Department of Animal Parasitology of the Veterinary Institute of the Universidade Federal Rural do Rio de Janeiro, Brazil. Clinical signs suggested a case of peritonitis. The cat's clinical condition was grave and death occurred within a few days. During necropsy, a brownish-red nematode, 24.9cm long, was found in the abdominal cavity and was identified as a male adult D. renale. This study reports the first confirmed case of dioctophymatosis in the domestic cat. The parasite's aberrant location in the abdominal cavity suggests that the domestic cat is not a suitable host.