The major carcass traits and chemical composition of muscle samples were evaluated in three age groups (6, 9 and 13 months) of nutria (Myocastor coypus). A total of 18 males and 18 females were weighed and slaughtered on the farm, then pelted, eviscerated and frozen. Intramuscular meat samples were taken from the loin and thigh muscles. The carcass yield (CY) was calculated and the total protein (TP), crude fat (CF) and crude ash (CA) content were determined in the laboratory on a dry matter basis. The average CY, without the head, was 53.3%, and was highest for 9-month-old animals (53.6%). In females, the average CY was slightly higher (52.9%) than for males (51.8%). The mean TP content in meat was approximately 21.7% in the loin and 21.1% in thigh muscles. The intramuscular CF content was higher in thigh samples. Older animals had a higher CF content and the CF content was lower in males than in females.