A study was conducted in an organized farm to know the prevalence status of subclinical mastitis. Screening of animals for subclinical cases was done by using TANUCHEK-SCC kit developed by TRPVB, TANUVAS Chennai. A total of 167 quarters from 46 lactating dairy cattle were screened for mastitis. Out of these, 42 samples were found positive for subclinical mastitis and none of the samples were found positive for clinical mastitis with visible changes. The positive samples for subclinical mastitis were further subjected for invitro antibiotic sensitivity test using antibiotic discs like ceftizoxime, amoxicillin/ sulbactam, ceftriaxone, enrofloxacin, cefalexin, gentamicin and cefoperazone/ tazobactum. Antibiogram studies revealed enrofloxacin (100 per cent) is the most sensitive drug followed by gentamicin (97.6 per cent), amoxicillin/ sulbactam (90.4 per cent), cefalexin (76.2 per cent), ceftriaxone (59.5 per cent), cefoperazone/ tazobactum (38.1 per cent) and ceftizoxime (35.7 per cent). In the study, Enrofloxacin was the sensitive antibiotic found against subclinical cases.