Background <p>Inmate suicide is a serious problem faced by society. Evidence shows that nature exposure is closely related to the mental health of inmates, yet its relationship with suicidal tendency remains unclear. Our study explores the relationship between nature exposure and suicidal tendency among inmates by establishing a moderated mediation model.</p> Methods <p>We conducted a survey from May to June 2022 in six Chinese prisons, utilizing tools including the Nature Exposure Scale, the short-form UCLA Loneliness Scale, the Suicide Orientation Subscale, and the Prison Group Climate Instrument, resulting in the collection of 1048 valid data. The study employed path analysis, implementing linear regression via the PROCESS program, to assess the mediation and moderation effects within our study variables.</p> Results <p>This study found that loneliness mediates the relationship between nature exposure and suicidal tendency among inmates. Additionally, the group atmosphere played a moderating role. Specifically, the more positive the group atmosphere in prisons, the better the mitigating effect of nature exposure on loneliness, and the weaker the promoting effect of loneliness on suicidal tendency.</p> Conclusions <p>Our findings offer valuable perspectives on mitigating suicide among prison populations. Prisons should consider increasing natural elements in inmates’ living, working, and activity spaces, and regularly evaluate and intervene in their loneliness. Additionally, improving the group atmosphere within the prison can help alleviate suicidal tendency.</p>