Objective: The objective of this study was to estimate the phytochemical constituents of the methanol leaf extract of Acanthus ilicifolius and to examine reducing power with antioxidant activity of the extract by in vitro method. Methods: Leaf extract was prepared by maceration method. Then the qualitative and quantitative phytochemical analysis of these extracts was carried out by applying standard procedures. Reducing power of the prepared extract was determined by Oyaizu method. In order to determine the in vitro scavenging ability of the extract against free radicals, anti-oxidant activity was determined by DPPH method. Results: The extract was found to be rich in phytochemicals. The content of alkaloids and saponins was 16.26 ± 0.22%, 3.82 ± 0.06% respectively. The total phenolics (292.62 ± 0.50mg/g of GAE) and flavonoids (44.15 ± 0.30 mg/g of QE) was found to be higher in this extract. It showed that the plant extract had a higher level of antioxidant and reducing property even at lower concentrations due to its hydrogen donating capability. Conclusion: The present study proves that the methanol leaf extract of Acanthus ilicifolius is a potent antioxidant and having high reducing power. Hence this extract found to be a valuable source of drugs to treat diseases caused by oxidation. © 2015, International Journal of Pharmacognosy and Phytochemical Research. All rights reserved.