In the processing industry a ratio of 4 to 12% of the total mass from guava is discarded in the form of bark and seeds obtained from the stages of cutting and pulping. The agro industrial by-products are a source of phenolic compounds with antioxidant action. Studies conducted how antioxidant potential investigation of phenolic compounds can contribute with the inclusion of this matrix in the human diet in the form of processed products or drugs. Therefore, the present study aimed to verify the antioxidant potential of the by-product obtained by processing guava Paluma compared to the fruit, quantifying the phenolic compounds and evaluating the ability of the extracts to scavenge free radicals. Phenolic compounds were obtained by sequential extraction with 80% hydroacetonic solution (v.v-1), hexane and ethyl acetate being homogenized, centrifuged, evaporated at 45°C and re-suspended in deionized water. The concentration of total phenolics, flavonoids and tannins was determined by colorimetric methods and reading held at specific wavelength for each compound being expressed in mg gallic acid.g-1 (phenolic) and mg catechin.g-1 (flavonoids and tannins). Antioxidants tests were performed by radical scavenging activity of DPPH, ABTS and ORAC being expressed in µmol of Trolox.g-1. The by-product from guava processing presented higher levels of total phenolic compounds and tannins than the fruit (2.60 > 2.16 mg GAE.g-1 and 0.031 > 0,008 mg catequina.g-1, respectively). The antioxidant activities ranged from 14.94 to 126.29 µmol TE.g-1 being a greater potential found in by-product by DPPH and ORAC assays, highlighting the lipophilic compounds which exhibited high antioxidant activity by ORAC method. These results reinforce the need to use the agro industrial by-product from guava as source of extraction and/or ingredient in the food industry or supplement in drug products in order to take advantage of its antioxidant potential.