I.Background: Male infertility is a global issue with few remedies, particularly for testicular damage caused by radiation. Investigating new medications to treat radiation-induced testicular damage was the goal of this study. II.Methods: Six male mice (n = 6) received 0.5 Gy whole-body irradiation for 5 consecutive days and were then intraperitoneally injected with telmisartan (1.2 mg/kg). The therapeutic effect of telmisartan was evaluated using quantitative real-time PCR. A drug affinity reactivity target stability (DARTS) assay was used to identify target proteins and pathways. Western blot, CCK-8, EdU 594 and ubiquitination assays were used to investigate the mechanism involved. Finally, rescue experiments were performed by combining telmisartan with ESR1 antagonists and agonists. III.Results: The telmisartan treatment group presented significantly higher mRNA levels of spermatogenic cell markers than did the irradiation treatment group (P < 0.05). The DARTS assay and Western blotting results revealed that telmisartan increased the expression of connexin in Sertoli cells and increased proliferation and activated downstream signalling pathways by controlling ESR1 expression. Ubiquitination pull-down assays revealed that the degradation of ESR1 after irradiation was inhibited by telmisartan. Telmisartan combined with PPT/AZD9496 further upregulated ESR1 expression, which was beneficial for reducing radiation-induced testicular injury. IV.Conclusions: In conclusion, our findings suggest that telmisartan reduces radiation-induced testicular damage in mice by upregulating ESR1 in Sertoli cells. These findings may lead to the development of new approaches for treating testicular damage caused by radiation.