Organoselenium compounds have promising antioxidant activity, anxiolytic-like, and antidepressant-like proprieties. Additionally, some pharmacokinetics propriety of drugs are increased when phosphorus is added to their structure. Thus, this study hypothesized to test the antioxidant activity of compounds using selenium and phosphorus on its structures using five phosphoroselenoates: O,O-Dimethyl Se-phenyl phosphoroselenoate (3a), O,O-Dibutyl Se-phenyl phosphoroselenoate (3c), O,O-Dibenzyl Se-phenyl phosphoroselenoate (3d), O,O-Dimethyl Se-(p-tolyl) phosphoroselenoate (3f), Se-(4-Methoxyphenyl) O,O-dimethyl phosphoroselenoate (3g), that may act against oxidative stress in biological systems. Antioxidant evaluation of phosphoroselenoates was investigated in the concentration of 10, 50, 100 and 500 µM using dimethyl sulfoxide as a solvent and were performed on five in vitro assays: 2‐azinobis‐3‐ethylbenzothiazoline‐6‐sulfonic acid (ABTS), 2,2‐diphenyl‐1‐picrylhydrazyl radical (DPPH), ferric ion reducing antioxidant power (FRAP), inhibition of reactive species formation and thiobarbituric acid reactive species (TBARS) on cerebral tissue of mice. All procedures were approved by the guidelines of the Committee on Care and Use of Experimental Animal Resources of Federal University of Pelotas (13008-2020). The results were expressed as mean ± standard error of the mean and the data was performed using one-way analysis of variance followed by Tukey test. Phosphoroselenoates showed antioxidant activity by being able to scavenging ABTS and DPPH radicals, ferric-reducing ability, prevented lipidic peroxidation and formation of reactive species on different levels. From these compounds, 3g presented the most promising activity. In conclusion, phosphoroselenoates presented antioxidant effect in different assays, which could be beneficial in the treatment of diseases that have oxidative stress on their physiopathology.