An outbreak of avian tuberculosis was detected in chickens from a rural area of Chaco Province, northeastern Argentina. The hens were emaciated and presented granulomatous lesions of various sizes throughout the internal organs. The lesions observed in three necropsied birds consisted of granulomas containing alcohol/acid-fast bacilli. All the lesions found were diagnosed histopathologically as tuberculosis, Mycobacterium avium subsp. avium were isolated from the cultures and confirmed by polymerase chain reaction techniques.