In the present study, antifertility effect of ethanolic extract of Cassia fistula leaf on the fertile male albino rats was studied. The sperm count was significantly decreased when treated with extract. Similarly, the sperm vitality, sperm motility were also decreased after the treatment of Cassia fistula extract. The abnormalities of sperm were also increased in the Cassia fistula extract treated rats. Thus the C. fistula may be used as a male antifertility agent.