The purpose of this study was to determine the influence of clinical mastitis on reproductive performance in first lactation holishtein cows in Vedio farm in Syria. Cows were divided as follows: group 1, clinical mastitis before first artificial insemination (n=34); group 2, clinical mastitis between first artificial insemination and pregnancy (n=19); group 3, clinical mastitis after confirmed pregnancy (n=13); and group 4, control cows (n=23) with no clinical mastitis. The number of days to first AI was significantly greater for cows with clinical mastitis before first AI (99.3 d) than for all other groups Gr2 (77.8 d), Gr3(75.7 d ) and Control(76.5 d). Artificial inseminations per conception were significantly greater for cows with clinical mastitis after first Artificial inseminations Gr2(3.68) than for cows with clinical mastitis before first Artificial inseminations Gr1 (2.3), cows with clinical mastitis after confirmed pregnancy Gr3(2.07) or cows with no clinical mastitis Control (2.04). The number of days to conception for cows with clinical mastitis after first AI Gr2 (151.7 d) was significantly greater than that for control cows (95.6 d), for cows with clinical mastitis before first Artificial inseminations Gr1(118.1 d) and that for cows that developed clinical mastitis after confirmed pregnancy (98.5 d). Clinical mastitis during early lactation markedly influenced reproductive performance of holishtein cows in Vedio farm in Syria.