Trials were conducted to evaluate the influence of vitamin B₂, ascorbic acid and melatonin on the reproductive performance of 42 healthy pluriparous mature cross (3/8 Finnish × 5/8 Rahmani) ewes during summer. Ewes were allocated into 4 groups: the first group (G₁; n = 11, 18–27 mo, 36–41 kg, BCS = 3) injected with 2mL saline, served as control. The second (G₂; n = 10, 20–31 mo, 34–40 kg, BCS = 3) and third group (G₃; n = 11, 19–28 mo, 35–42 kg, BCS = 3) were injected intramuscular daily for 3 wk with 2 mL (1 5mg) of vitamin B₂ and ascorbic acid, respectively. Ewes in the fourth group G₄ (n = 11, 22–29 mo, 33–39 kg, BCS = 3) received double daily subcutaneous injections of 0.5 mg melatonin at 8AM and 4PM at the dorsal surface of the ear. All treated groups (G₂, G₃, and G₄) received 1g zinc chloride and 2.5mg chromium (Merck Millipore, USA, Cat #. 1088161000 and 1120970500, respectively) orally with ration once per week for 3 weeks. All animals were checked for the onset of estrus 2 times daily using an intact ram and ewes were bred via natural mating using 3 rams. Reproductive performance parameters (onset of estrus, lambing rate and number of lambs) were recorded. Laparoscopic examinations were carried out throughout the study for detection of ovulation rates. Data are presented as means ± SEM and compared by Student’s t-test using SPSS program. Results revealed that, ascorbic acid had a significantly (P < 0.05) decreased mean interval (days) from treatment to estrus as compared with control group (15.73 ± 1.83 vs. 22.64 ± 2.50, respectively). A remarkable improvement in the lambing rate in G₂, G₃ and G₄ treated groups than in the G₁ (80.0, 90.9, 90.0 Vs. 72.7%, respectively). The highest proportion of ewes bearing single lamb observed in G₃ (100%). Incidence of lamb mortality found only in G₂ (triplet) in one ewe. The ovulation rate was significantly (P < 0.05) elevated in G₄ than that in G₂ and G₁ (1.60 ± 0.16 vs. 1.20 ± 0.13 and 1.14 ± 0.00, respectively). The follicular development did not vary among groups. In conclusion, vitamin B₂, ascorbic acid and melatonin have a beneficial effect on the reproductive performance of ewes during summer.