Objective To investigate the immunotoxicity effect of triphenyl phosphate (TPHP) on thymus tissue of mice, and analyze the related mechanism. Methods Specific pathogen free BALB/c mice were randomly divided into control group, low-, medium- and high-dose groups, with 12 mice per group (equal gender distribution). Mice in these four groups were orally administered doses of 0, 1, 10, and 150 mg/kg body weight of TPHP daily for 60 days. After the exposure, the complete blood count of mice was detected, thymus tissue was collected, coefficient of thymus organs was calculated, and the histopathology changes of thymus were observed. Real-time quantitative polymerase chain reaction was used to assess the expression of genes related to inflammation, oxidative stress, cellular autophagy, and apoptosis in thymic tissues. Results During the exposure period, male mice in the high-dose group had poor fur condition, whisker loss, and increased irritability, while these phenomena were not observed in female mice. At the end of the exposure period, there were no significant changes in mice body weight or thymus organ coefficients among the groups. However, male mice in the high-dose group showed cellular apoptotic changes in the thymic tissue. The amount of white blood cell, lymphocyte, neutrophil granulocyte, red blood cell distribution width, platelet and the plateletcrit of male mice was lower in the high-dose group than that in the control group (all P<0.05). The relative mRNA expression of interleukin (Il)-1β, Il-6, catalase (Cat), P62, as well as the ratio of B-cell lymphoma 2 (Bcl-2) associated X protein (Bax)/Bcl-2 in thymic tissue of male mice were higher in the low-dose group than that in the control group (all P<0.05). The relative mRNA expression of nuclear factor erythroid-2 related factor 2 (Nrf2), superoxide dismutase 1 (Sod1), glutathione peroxidase 1 (Gpx1), P62, as well as the ratio of Bax/Bcl-2 in the thymic tissue of male mice were higher in the medium-dose group than that in the control group (all P<0.05). The relative mRNA expression of Nrf2, Cat, Sod1, Gpx1, P62, cysteinyl aspartate specific proteinase-3, as well as the ratio of Bax/Bcl-2 in the thymic tissue of male mice were higher in the high-dose group than that in the control group (all P<0.05). The relative mRNA expression of Il-1β and the ratio of Bax/Bcl-2 in thymic tissue of female mice were higher in the low- and medium-dose group (all P<0.05), while the relative mRNA expression of interferon-γ, Nrf2, Cat, P62, microtubule-associated protein light chain 3, as well as the ratio of Bax/Bcl-2 in thymic tissue of female mice were higher in the high-dose group than that in the control group (all P<0.05). Conclusion Although TPHP exposure had not significantly affected the body weight, thymus organ coefficient and histopathology of mice, it induced changes in oxidative stress-related indicators in thymic tissue, promoted cellular autophagy, apoptosis, and inflammation in the thymic tissue, with observed gender difference.