Avian mycobacteriosis in poultry is a contagious disease and may also be called avian tuberculosis or avian TB. Several mycobacterial species can be involved in the aetiology of avian tuberculosis. However, avian tuberculosis is most often caused by Mycobacterium avium belonging to serotypes 1, 2, 3 and 6 and M. genavense. The capacity of M. avium to produce progressive disease may be related to cell wall constituents and certain complex lipids present in the cell wall such as cord factor, sulfur-containing glycolipids (sulfatides) or strongly acidic lipids. Clinical signs are not pathognomonic and vary depending on the organs involved. Mortality over a short period may be insignificant but the intermittent loss of adult birds in valuable breeding stock and decreased egg production in layers are detrimental. Avian Mycobacteriosis also has zoonotic importance and commonly affect the immunocompromised human. The various preventive and control measures are present to control this disease but the diagnosis of the disease is difficult and hence it remains uninvestigated in many parts of our country.