Mastitis is common in buffaloes with significant impact on the rural economy. The present work was undertaken to find out the prevalence of sub clinical mastitis in buffaloes in and around Gannavaram, Andhra Pradesh, India by using different diagnostic methods. The prevalence of sub clinical mastitis based on California Mastitis Test, somatic cell count, electrical resistance and milk pH was 20.34, 21.62, 6.20 and 8.27 percent, respectively on screening of 629 quarters of 158 Graded Murrah buffaloes. Bacterial culture was considered to be a gold standard and revealed the prevalence as 28.30 percent with 178 quarter milk samples positive for bacterial growth. Further the study was also focussed on the comparison of the diagnostic tests CMT, SCC, ER and pH by using culture results as gold standard. The percent accuracy of California Mastitis Test, Somatic cell count, electrical resistance and pH were 89.83, 92.69, 77.27 and 79.65, respectively.