Pasteurella multocida serotype A:3 has been mostly implicated in pneumonic pasteurellosis in ruminants. In contrast, our previous studies have reported that both serotypes A:1 and A:3 were responsible for respiratory diseases in cattle and buffaloes. However, the pathology and pathogenesis of P. multocida serotype A:1 (Pm A:1) infection have not been studied in ruminants. In the present study, 12- to 15-week-old buffalo calves (Bubalus bubalis) infected by Pm A:1 had fibrinous and suppurative bronchopneumonia with focal areas of coagulation necrosis typical of pneumonic pasteurellosis. For the first time, this study reports the lung pathology and pathogenecity of Pm A:1 infection in calves.