Exercise in a hot environment can lead to an increase in core body temperature and heat stress, which is associated with dysfunction of the lungs. The purpose of the present study was to investigate the effect of selenium consumption on the expression of Nf-kB and TLR4 in the lungs of rats after a period of exercise in a hot environment. In this experimental study, 32 male Wistar rats were divided into four groups: control, exercise in a normal environment, exercise in a warm environment, and exercise in a warm environment with selenium supplementation. Exercise was performed for eight weeks in a normal and warm environment. Selenium was administered as an oral supplement at a specific dose. At the end of the period, lungs tissue was sampled Nf-kB and TLR4 gene expression were measured. After confirming the normal distribution of the data, one-way analysis of variance was used to compare the groups and, if necessary, Bonferroni's test was used. The significance level was set at p<0.05. The results of the present study showed that NF-KB in the group exercising in a hot environment with selenium consumption had a significant decrease compared to the control group (p=0.004) and the group exercising in a normal environment had a significant decrease compared to the control group (p=0.043). Also, TLR4 in the group exercising in a hot environment with selenium consumption had a significant decrease compared to the control group (p=0.001) and the group exercising in a normal environment had a significant decrease compared to the control group (p=0.039). Training in a hot environment can lead to lung damage, but selenium supplementation plays an effective role in reducing these damages and improving physiological responses.