The aim of the present study was to investigate effects of onion juice on semen values of malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GPx) and total antioxidant status (TAS) compared to Zn sulfate in rats. One hundred and sixty-two Wistar male rats were randomly allocated into 9 treatment groups (each including 3 groups and 6 replicates). Group 1 served as control and received distilled water. In group 2, animals received 1 cc fresh onion juice. In group 3, rats were offered 2 cc fresh onion juice. Group 4 drenched 15 mg/kg zinc (Zn) sulfate. In group 5, rats were treated with 30 mg/kg Zn sulfate. Group 6 was offered 1cc fresh onion juice + 15 mg/kg Zn sulfate to experimental animals. In group 7, 1 cc fresh onion juice + 30 mg/kg Zn sulfate was provided to rats. Group 8 consumed 2 cc fresh onion juice + 15 mg/kg Zn sulfate. In group 9, animals provided 2 cc fresh onion juice + 30 mg/kg Zn sulfate. All groups were given treatments orally and ad libitum access to chow pellets and fresh water. After 4 weeks semen samples in cauda epididymis were used to determine MDA, SOD, GPx and TAS levels. According to the data, sole onion juice significantly decreased semen MDA level (P < 0.05). Also, a combination between the administration of onion and Zn significantly attenuated sperm MDA (P < 0.05). Sperm GPx level in the co-administration of onion and Zn was significantly altered (P < 0.05). Results suggest that presumably onion juice protects from semen oxidation in rat testes.