Abstract: The effects of Sub-lethal treatments (20 and 60% of 24 h LC50) of chlorophyllin on the reproduction and development of Lymnaea acuminata has been studied. There was a significant decrease in the fecundity, hatchability and survival of the young snails. Treatment with 60% of 24 h LC50 of chlorophyllin caused minimum fecundity (57 eggs/20 snails, 48 h) in summer (sunlight). After 48 h no egg laying and hatching was noted in snails exposed to 60% of 24 h LC50 of chlorophyllin in both winter (sunlight) as well as in summer (sunlight). Development could not proceed beyond the veliger stage due to the death of the embryo. The developmental arrest was noticed in many egg strings leading to the high rate of mortality and there by reduction in hatchability of the eggs. Growth rate of survived snails was also very slow. This present study clearly shows that the efficacy of chlorophyllin gives significant control of reproduction of the snails even at sub-lethal exposure. The use of the natural products would have an added advantage against aquatic snails as it would be non toxic to the non target animals and less hazardous to the environment.