A longitudinal observational study on calf morbidity and mortality was conducted in smallholder dairy farms in Ada'a Liben district of Oromia, Ethiopia. A total of 185 calves from 112 market oriented smallholder dairy farms were selected randomly and regularly monitored for clinical health problems up to six months of age. Information on potential risk factors was collected by personal observation during the regular visit to farms and from questionnaire survey conducted during the study period. The overall incidences of crude morbidity and crude mortality were 62% and 22%, respectively. The most frequent disease syndrome was calf diarrhea with the incidence of 39% followed by joint ill 6%. The other disease conditions/syndromes diagnosed include navel ill, pneumonia, septicemic conditions, congenital problems and miscellaneous cases. Age of the calves, age at first colostrum ingestion and cleanness of the calf barns significantly influenced morbidity. Older calves (greater than three months of age) were at lower risk of crude morbidity than younger calves (less than three months of age) (HR = 0.42, P = 0.001). Higher risk of crude morbidity was observed in calves that ingested their first colostrum meal later than 6 hours of age compared to those that ingested colostrum earlier (HR = 2.24, P = 0.001). Similarly, calves housed in unclean barns were at higher risk of morbidity than calves housed in clean barns (HR = 1.75, P = 0.024). Of the 20 potential risk factors investigated, age was the only factor that was found significantly associated with mortality (HR = 0.04, P = 0.001). Calves older than three months of age were at lower risk of mortality than younger calves.