Phenolics are the most abundant secondary metabolites of plants that are widely distributed in the plant kingdom. In the last few years, the development and identification of phenolic compounds from various plants have become a major area of the environment and health-related research. In the present study, different phenolic compounds were purified from the bark of the medicinally important plant Acacia nilotica which is rich in polyphenols and were evaluated for their insecticidal potential against a polyphagous pest, Spodoptera litura (Fab.). The compounds viz. Catechin, Chlorogenic acid, and Umbelliferone were purified from ethyl acetate-acetone (E-AE) fraction using Semi-preparative HPLC and were identified using melting point determination, Nuclear Magnetic Resonance (NMR), and Mass Spectroscopy (MS). These phenolic compounds recorded detrimental effects on the growth and development of second instar larvae (6 days old) of S. litura. The larval growth, survival, adult emergence, pupal weight, and different nutritional indices were adversely affected by the various concentrations of these purified compounds. The findings revealed the insecticidal potential of polyphenols obtained from the bark of A. nilotica, which can provide an alternative for resistance management, as these plant phytochemicals are highly effective against insecticide-resistant insect pests.