Abstract: Cross-sectional study design was applied from March 2017 to February 2018 to determine the prevalence rate of mastitis at quarter and cow level in smallholder dairy farms in selected area of Gurage zone, South Ethiopia. Various correlated animal and environmental factors to mastitis were also investigated. Among 333 totally investigated lactating cows (75 zebu and 256 cross breeds), overall prevalence of mastitis at cow level was found to be 199 (59.8%) of which 62(31.2%) and 137(68.8%) were identified as positive for clinical and subclinical forms of mastitis respectively.