Effect of feeding Tulsi leaves along with the normal diet, on the reproductory behaviour of adult male Wistar rats, was studied. Experimental animals were given Tulsi extract in graded doses of 100 mg/kg, 150 mg/kg, 200 mg/kg, and 400 mg/kg along with the normal diet while control group only had similar normal diet. Each dose was given for 15 days and reproductory behaviour monitored in terms of score, on every alternative day. There was significant decrease in sexual behavioural score, when Tulsi leaves extract dose was increased to 200 mg/kg and 400 mg/kg.