Background: Cigarette smoke can trigger oxidative stress. An alternative to overcome the harmful effects of cigarette smoke is through antioxidants. White oyster mushrooms (Pleurotus Ostreatusostreatus or P. ostreatus) are a source of exogenous antioxidants because many contain active compounds for potential antioxidants such as phenol and flavonoid compounds. The purpose of this study was to analyze the effect of ethanolic extract of Pleurotus P.ostreatus on 4-hydroxy-2-nonenal (HNE) and glutathione (GSH), as well as to analyze their correlation in the lung of Wistar male rats exposed to cigarette smoke. Methods: The study was a preclinical experiment conducted on 24 rats divided into four groups. The treatment was carried out for 42 days and antioxidant effects were assessed through levels of HNE and GSH in rat lungs. Groups were divided as follows: I- normal control, II- negative control, III and IV exposed to cigarette smoke for 60 minutes/day. Group III (treatment group) was treated with ethanolic extract of PleurotusP. ostreatus at 250 mg/kg BW rat/day, and group IV (comparison group) was treated with N-acetyl cysteine 600 mg /day. Data analysis used was one-way ANOVA and Kruskal Wallis test, and Spearmen rank correlation coefficient test. Results: The results showed that the group receiving ethanolic extract of PleurotusP. ostreatus had HNE levels of (44,18 ± 2,09 pg/mL) and GSH (0,04 ± 0,00 pg/mL) protein. This extract significantly increased GSH levels and inhibited the increase of HNE levels. Results of GSH (p≤0.01) showed significant results using one-way ANOVA. Conclusions: The ethanolic extract of P. ostreatus can prevent lipid peroxidation and decrease endogenous antioxidant levels in lung cells exposed to cigarette smoke. Ethanolic extract of PleurotusP. ostreatus has good antioxidant potential.