Two diamond doves (Geopelia cuneata) in a flock of 23 birds housed in an aviary in a zoo in central Japan were found dead as a result of mycobacteriosis. Fecal samples of the remaining doves were positive for mycobacterial infection, and thus they were euthanatized. Clinical signs and gross pathology, including weight loss and sudden death and slight enlargement of the liver and intestine, were observed in a small number of birds (3/23). Disseminated histiocytic infiltration of either aggregates or sheets of epithelioid cells containing acid-fast bacilli, in the absence of caseous necrosis, were observed in different organs of the infected doves, especially lungs (23/23), intestines (9/23), livers (7/23), and hearts (6/23). Mycobacterium sp. was isolated from the livers of three birds (3/23). DNA extracted from frozen liver and formalin-fixed, paraffin-embedded tissues (5/23) were used for amplification of the gene encoding mycobacterial 65-kDa heat shock protein (hsp65). The causative Mycobacterium species was identified by PCR-restriction fragment length polymorphism analysis. Mycobacterium genavense infection was confirmed in three of the diamond doves. Moreover, partial 16S rDNA gene sequencing revealed 100% identity across the three samples tested, and 99.77% nucleotide homology of the isolate sequence to M. genavense. The main route of M. genavense infection in the diamond doves was most likely airborne, suggesting a potential zoonotic risk of airborne transmission between humans and birds.