Paraquat (PQ) is an agrochemical agent commonly used worldwide, which can cause acute lung injury (ALI) and death. Hyperbaric oxygen treatment (HBOT) is a therapeutic method, but the mechanisms of the protective effect of HBOT on ALI remain elusive. The purpose of this study was to evaluate the effect of HBOT on acute lung injury induced by PQ in rats. Wistar Albino rats (n=21) were separated into three groups of seven animals each: control (C), PQ, and PQ + HBOT groups. 20 mg/kg PQ was administered intraperitoneally in PQ and PQ + HBOT groups to induce experimental lung injury. Three days after PQ treatment, PQ + HBOT group was administered 100% O-2 at 2.0 ATA for 1 hour per day, for five consecutive days. At the end of the study, lung tissue was obtained for determining total oxidant status (TOS), total antioxidant status (TAS), oxidative stress index (OSI) and histopathological determination. Tumor necrosis factor-alpha (TNF-alpha), interleukin 6 (IL-6), basic fibroblast growth factor (bFGF), transforming growth factor (TGF)-beta 1 mRNA levels were assessed by quantitative reverse transcription-polymerase chain reaction. In addition, the inducible nitric oxide synthase (iNOS) level in the plasma was determined. Plasma iNOS, OSI, tissue TNF-alpha, TGF-beta 1 and bFGF mRNA levels, and histological injury scores in PQ + HBOT group were significantly lower than PQ group. TAS level in PQ + HBOT group was significantly higher than PQ group. The findings suggest that HBOT could effectively ameliorate PQ-induced lung injury in rats.