Meat tenderization can be affected by a variety of factors including animal age. However, results obtained from goose, chicken, turkey, and ostrich studies have shown that the effects of age on meat tenderization were insignificant, which may be due to a very limited age difference in birds used in those studies. Therefore, the purpose of this study was to investigate the effects of animal age on postmortem proteolysis and tenderization of breast muscle from developing and mature White Roman geese. Goose carcasses from mature (50 mo old, n = 10) and young (3 mo old, n = 10) geese were vacuum-packaged and stored at 5°C within 10 min postmortem. Breast (pectoralis major) samples were taken at 0 (∼10 min postmortem), 1, 3, and 7 D of storage. Our results showed that the decrease in pH, calpain-1 and -11 activities, desmin content and shear force, as well as the increase in myofibrillar fragmentation index were more rapid (P < 0.05) in young than in mature goose breast. These results suggest that postmortem proteolysis and tenderization of goose muscle are extensively affected by age.