ObjectiveThe aim of this study was to determine the prevalence and associated factors of postpartum depression among mothers who gave birth within the last 12 months among hospitals of Southwest Ethiopia, 2017.ResultThe study revealed that 138 (33.82%) of mothers had postpartum depression. Unplanned pregnancy adjusted odds ratio (AOR) = 4.49, 95% CI (2.31, 8.71), age from 15 to 24 years AOR = 0.420, 95% CI (0.18, 0.98), having a chronic physical illness AOR = 7.71, 95% CI (2.34, 25.44), experiencing death of infant AOR = 4.12, (1.78, 9.51) and unstable marital condition AOR = 6.02, (2.79, 12.99) were significantly associated with postpartum depression. The prevalence of post-partum depression was found to be high. Therefore urgent attention must be given to this problem, in particular towards its early detection, so that morbidity could be reduced in this group of women.