Cestrum nocturnum is a terrestrial plant of Solanaceae family containing many biologically active Phytochemicals. In present study, leaves were extracted with methanol to obtain dried methanolic extract of plant. Bioassay experiments were conducted to determine insecticidal molluscicidal and piscicidal activity. LC50 and LC90 values were determined for 24 hr and 48 hrs. Behavioral responses were also noted during exposure to elaborate the toxic nature of the extract. It shows a promising biocidal activity on snail Lymnea accuminata and fish Poecilia reticulata. Possibly saponin content present in extract is responsible for the death of these aquatic organisms. Further purification of this extracts may lead to the emergence of novel insecticide, ecologically safe piscicide , and molluscicide to kill trash fishes and snails in aquaculture.