Abstract: The species Guazuma ulmifolia Lam., popularly known in Brazil as chico-magro, belongs to Sterculiaceae, is used in the form of a tea as hypolipidemic and to reduce weight. In this work, antioxidant potential, total phenolic and flavonoids contents from the stem bark of the plant were investigated. Antioxidant potential was determined using DPPH assay. Total phenolic was measured using Folin-Ciocalteu and total flavonoid, using aluminium chloride. The stem bark of G. ulmifolia exhibited high antioxidant capacity, as well as a large content of phenolic and flavonoid compounds. IC50 obtained with DPPH assay varied from 8.09±0.14 to 67.69±0.31 μg mL-1. Total phenolic varied from 160.00±0.71 to 373.44±0.36 mg g-1 DF (Dry Fraction) and flavonoid contents, from 23.50±0.48 to 33.20±0.27 mg g-1 of DF. Results obtained indicated that the stem bark extracts and fractions from G. ulmifolia have a good potential to prevent disease caused by free radicals and also might be used as a potential source of natural antioxidant agents.