Background and objectives: Ischemia-reperfusion (IR) caused by infrarenal abdominal aorta cross-clamping is an important factor in the development of ischemia-reperfusion injury in various distant organs. Materials and Methods: We investigated potential antioxidant/anti-inflammatory effects of thymosin beta 4 (T4) in a rat model of abdominal aortic surgery-induced IR. T4 (10 mg/kg, intravenous (i.v.)) was administered to rats with IR (90-min ischemia, 180-min reperfusion) at two different periods. One group received T4 1 h before ischemia, and the other received 15 min before the reperfusion period. Results: Results were compared to control and non-T4-treated rats with IR. Serum, bronchoalveolar lavage fluid and lung tissue levels of oxidant parameters were higher, while antioxidant levels were lower in the IR group compared to control. IR also increased inflammatory cytokine levels. T4 reverted these parameters in both T4-treated groups compared to the untreated IR group. Conclusions: Since there is no statistical difference between the prescribed results of both T4-treated groups, our study demonstrates that T4 reduced lung oxidative stress and inflammation following IR and prevented lung tissue injury regardless of timing of administration.