OBJECTIVE Increased generation of free radicals exceeding the antioxidant capacity of the host is deleterious. Thus new, potent, and safe antioxidants will be a valuable addition to the limited antioxidant arsenals available. Therefore, the antioxidant activity, cytotoxicity potential, and phytochemical constituents of the methanol extract of Spondias mombin seed (MESSM) were investigated. METHODS 2,2-diphenyl-1-picrylhydrazyl (DPPH), nitric oxide (NO), and hydrogen peroxide (H2O2) were the antioxidant assays used. The cytotoxicity of MESSM was evaluated against a rhabdomyosarcoma (RD) cell line in a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide based assay. The phytochemical constituents of MESSM were identified using gas chromatography-mass spectrometry. RESULTS MESSM produced better antioxidant activity in the DPPH (IC50=58.64±1.49 μg/mL) and H2O2 (IC50=44.03±5.57 μg/mL) assays than in the NO (IC50=494.55±12.68 μg/mL, p<0.0001) assay. Moreover, MESSM was nontoxic (CC50=139.6±0.54 μg/mL) in comparison to cyclophosphamide (CC50=0.97±0.03 μg/mL) against the RD cell line. The major compounds in MESSM were dodecanoic acid (22.48%), tetradecanoic acid (17.95%), n-hexadecanoic acid (15.35%), capsaicin (12.11%), and dihydrocapsaicin (5.23%). CONCLUSIONS The seed extract of Spondias mombin contains nontoxic antioxidant compounds that could be explored in the pharmaceutical and cosmetics industries for the development of antioxidant agents.