Background: Both clomiphene citrate and tamoxiphene citrate, as an anti estrogen, is the most common prescribed medication for male infertility.In humans, ant estrogens interfere with the normal negative feedback of sex steroids at the hypothalamus and pituitary, thereby increasing endogenous gonadotropin releasing hormone (GnRH) secretion from the hypothalamus and follicle stimulating hormone (FSH) and luteinizing hormone (LH) secretion directly from the pituitary. Objective: The objective of this study was to investigate the effect of clomiphene citrate (CC) and tamoxiphene citrate (TC) administered to male mice on quality of sperm motility and activity. Materials and Methods: Ninety six male mice were divided into two major groups, and every one of these groups was subdivided into three minor groups involving control and two treated groups. In the CC study, 48 mice were administrated orally 0, 0.0125 mg and 0.025 mg as control (G 1), low dose (G 2) and high dose (G 3) for 42 days. While, in the TC study, 48 mice were administrated orally 0, 0.01 mg and 0.02 mg as control (G 1), low dose (G 2) and high dose (G 3) for 42 days. Then, the male mice were sacrificed, both vas deferens were collected and assessment sperm motility and activity. Results: The results of present study appeared that the use high dose of CC or TC significantly increment (P<0.05) sperm motility and activity as compared to control groups. Conclusions: Based on the results of this study, it can be concluded that the administration of high dose of either CC or TC increases sperm motility and activity.