Humanity has employed medicinal plants as a source of medications for many thousands of years. The evergreen flowering tree plant Simarouba amara is also known as bitterwood, dysentery barks, Laxmi Taru, and paradise tree. It uses its seeds to make edible oils. Mosquitoes spread a wide range of illnesses like malaria, yellow fever, dengue, filariasis, and chikungunya in addition to the terrible biting nuisance. The effectiveness of plant extracts against mosquito larvae has been the subject of numerous studies worldwide. The goal of the current study was to evaluate the phytochemical composition, larval and pupal toxicity, ovicidal activity, adulticidal activity, and repellant efficacy of Simarouba amara oil against the malaria vector Anopheles stephensi. Phytochemical analysis of S. amara oil revealed the presence of alkaloids, flavonoids, phenols, tannins, proteins, carbohydrates, steroids, Triterpenoids. GC/MS analysis identified at least 7major bioactive compounds in the S. amara oil. In mosquitocidal bio-assay, LC50 of S. amara oil against An. stephensi larvae and pupae were 231.185 ppm (larva I), 267.066 ppm (II), 301.830 ppm (III), 356.892 ppm (IV), and 435.970 ppm (pupa). In ovicidal assay, egg hatchability was reduced by 100% after treatment with 400 ppm of S. amara oil. In adulticidal assays the LC50 values were 332.375ppm for 50% of adult mortality of An. stephensi, and repellant efficiency of S. amara oil against An. stephensi were repellant by 64% after the treatment of 100ppm. Overall, our results highlighted that S. amara oil could be useful candidates to develop bio-formulated mosquitocidal effective against malarial vector, An. stephensi.