The aim of this study was to reduce embryonic loss and improve conception rates in lactating ewes during transition to breeding season through post-mating administration of carprofen. An intravaginal sponge containing 60 mg medroxyprogesterone acetate (Esponjavet®, Hipra, Turkey), was administered in all Assaf ewes (n = 126) for a period of seven days. The vaginal sponge was then removed and 450 IU of eCG and 10 mg/ewe of PGF2α were injected intramuscularly. The rams were introduced to the flock at a ratio of 1:6 (i.e. 1 ram per 6 ewes) for a 5-day mating period. After the withdrawal of the rams, the ewes were randomly divided into two groups: the carprofen group (n = 55) and the control group (n = 71). The ewes of carprofen group received a dose of carprofen (1.4 mg/Kg s.c.), whereas those of control group received saline (1 mL) on day 6 after the end of estrus synchronization. The diagnosis of pregnancy was performed on day 35 following the removal of the ram using real-time ultrasonography. The results indicated that the conception rate was significantly higher in the carprofen group (65 %, 36/55) than in the control group (47 %, 34/71) (P < 0.05). The rate of multiple pregnancies was 30 % (11/36) in the carprofen group and 12 % (4/34) in the control group, while the mean number of fetuses per pregnancy was recorded as 1.30 and 1.11, respectively (P > 0.05). In conclusion, the post-mating administration of carprofen, a non-steroidal anti-inflammatory drug with a prolonged half-life, has been found to improve conception rates in ewes.