Annona squamosa Linn. (custard apple) has been used extensively in India traditional medicine for treatment of dysentery, cardiac problems, fainting, worm infections, constipation, hemorrhage, dysuria, fever. This study assessed the phytochemicals present in the leaves of A. squamosa. The phytochemical was extracted separately with distilled water and 96% ethanol. A wide variety of pharmacologically active compounds such as alkaloids, coumarins, tannins, cardiac glycosides, flavonoids, carbohydrates, phenols, and saponins were found to present in the leaves of A. squamosa. However, terpenoids and phlobatannins were absent in this plant. This study also assessed the contents of phenolics and flavonoids for their in vitro antioxidant activity. The total polyphenol content of ethanol extract of A. squamosa measured by Folin-Ciocalteau reagent in terms of gallic acid equivalent achieved 242.88±6.13 mg GAE/g. The flavonoid content of the plant sample as quercetin equivalent achieved 82,61±0.82 mg QE/g. The antioxidant activity of the ethanol extract of A. squamosa was correlated with total phenolic and flavonoid content with values IC50 of 132.96±1.33 μg/ml, 64.74±0.52 μg/ml for DPPH and ABTS scavenging activity, respectively.