Monitoring circulating pathogens in wildlife populations is important in evaluating causes and sources of disease as well as understanding transmission between wild and domestic animals. In spring 2010, a sudden die-off in a chamois (Rupicapra rupicapra) population sharing habitat with livestock occurred in northeastern Austria. Nineteen animals were submitted for examination. Necropsy and pathohistologic and bacteriologic results yielded lesions associated with Pasteurellaceae species. Additional testing included enterobacterial repetitive intergenic consensus and random amplification of polymorphic DNA PCR analysis to evaluate the circulating strains. The isolated strains were most closely related to Mannheimia glucosida and Bibersteinia trehalosi. Reports of mass mortalities in chamois due to pneumonia have been reported previously in the northern Alpine area of Italy. To the authors' knowledge, this is the first report of acute mortality due to strains of Mannheimia and Bibersteinia in Austrian chamois.