L-arginine is an amino acid, which serves as the sole substrate for nitric oxide (NO) synthesis with the concomitant formation of L-citrulline in biologic system. NO has been demonstrated to be involved in smooth muscle relaxation and vasodilation, immune regulation and neurotransmission. It also has an important function as both intercellular and intracellular signals in many physiological systems, including the reproductive system where NO mediates penis erection. This study was undertaken to determine the effects of L-arginine on sperm motility, sperm count, and the nitric oxide level in the seminal plasma. Twelve sexually matured male rabbits (Oryctolagus cuniculus) were randomly divided into four groups with three rabbits each, which were control, low, medium, and high concentration groups. The treatment groups were force-fed with 100mg/kg, 200mg/kg, and 300mg/kg body weight of L-arginine for four weeks, whereas the control group was force-fed with water. Semen samples were collected every three days alternatively for a week before starting treatment and then after four weeks of treatment. Pre-treatment and post-treatment results were compared. Semen samples were collected using artificial vaginas from each group for sperm analysis such as sperm motility, sperm count and NO level in seminal plasma. Sperm motility and sperm count were analysed manually under microscope (twenty power objective), using a Makler counting chamber. NO levels in the seminal plasma were determined using Griess reaction. The results obtained from this study showed that oral consumption of L-arginine exerted a significant (p