Objective The alcoholic extract of stem bark of Terminalia arjuna (ALTA) was screened for antioxidant and antimutagenic (anticlastogenic) activity. Methods Antioxidant property was determined by 1, 1, Diphyny l, 2-Picryl hydrazyl (DPPH) assay, super oxide radical scavenging activity, lipid peroxidation assay and total polyphenolic content was determined by Folin-Ciocalteau's reagent. Antimutagenic activity was evaluated using micronucleus test in mice. Results The ALTA has shown potent antioxidant activity with EC50 of 2.491±0.160, 50.110±0.150 & 71.000±0.250 in DPPH assay, superoxide radical scavenging activity and lipid peroxidation assay, which is comparable with ascorbic acid with EC50 of 2.471±0.140, 40.500±0.390 and 63.000±0.360 respectively. In micronucleus test, ALTA (100 & 200mg/kg, p.o.) showed significant reduction in percentage of micronucleus in both polychromatic erythrocytes (PCE) and normochromatic erythrocytes (NCE) and also shown significant reduction in P/N ratio. Conclusions These results suggested that ALTA possess significant antioxidant and antimutagenic activity.