Piscicidal action of distilled water, 50% ethyl alcohol, methanol and acetone extracts of three indigenous plant seeds Jatropha carcus (Linn.),  Hydnocarpus wightianus (Blume) and Aleurites moluccana (Linn. Willd) were tested for the first time upon the live Cichlid fish, Tilapia Oreochromis niloticus (Linn.) collected from a local fish hatchery. The fishes exhibited different types of behavior in different concentrations of the seed extracts, such as hyperactivity, erratic swimming, frequent gulping of air, loss of movement, ultimately leading to death. Fish mortality percentage varied in accordance with plant seeds, solvents and concentrations. According to mortalities %, the extent of toxicity of the solvents for J. carcus, H. wightianus and A. moluccana seeds on O. niloticus was ranked in the following order: Acetone > methanol > 50% ethyl alcohol > distilled water. To determine the LC₅₀ of the seed extracts, the relationship between observed and expected mortalities of the fish and dose-mortality relationships, probit calculation, chi-square and ANOVA tests were done. Based on the LC₅₀ values, the relative toxicity of the seed extracts was recorded in order: J. carcus>H. wightianus>A. moluccana. The most toxic was the acetone extract of J. carcus seed, whereas the least toxic was distilled water extract of A. moluccana seed. These plant seed extracts may be useful to remove the unwanted weed fish species from the fish culture ponds.