Objective: The present study was undertaken to evaluate the phytochemical constituents and antioxidant and free radical scavenging properties of Clerodendron glandulosum.Coleb.Methods: - Methanolic extract of C.glandulosum.Coleb (MECG) was studied for its qualitative and quantitative phytochemical constituents and free radical scavenging potential using different in vitro assays for hydrogen peroxide, hydroxyl, superoxide, DPPH, nitric oxide, peroxynitrite, singlet oxygen and hypochlorous acid radicals scavenging assays. Its lipid peroxidation inhibitory activity, metal chelating activity and reducing power were also assayed.Results: Qualitative phytochemical screening of MECG showed presence of polyphenols, steroids, flavanoids and saponins. Quantitative phytochemical analysis revealed 34.3±0.89 mg/ml gallic acid equivalent-polyphenols, 46.1±1.00 mg/ml quercetin equivalent-flavanoids and 53.36±0.93 mg/ml ascorbic acid per 100 mg MECG. The MECG scavenges hydrogen peroxide (IC50 120.23± 1.53 ?g/ml), hydroxyl (IC50 70.23±1.36 ?g/ml) superoxide (IC50 80.36±1.36 ?g/ml), DPPH (IC50 50.11±1.36 ?g/ml) and nitric oxide (IC50 90.11±1.55 ?g/ml) radicals in a dose dependent manner. The IC50 values for peroxynitrite, singlet oxygen and hypochlorous acid were 48.41±1.72, 62.15±1.69 and 136.69±2.01?g/ml, respectively. MECG also inhibited lipid peroxidation (IC50 150.56±3.02 ?g/ml) and promoted metal chelation (IC50 50.29±2.00 ?g/ml) in a dose-dependent manner. Assay of reducing capacity of MECG showed a dose-dependent response.Conclusion: The results suggest that a methanolic extract of Clerodendron glandulosum.Coleb possesses a strong antioxidant activity against all known radicals and can be considered as a natural antioxidant.