Introduction <p>Population ageing has altered the health profile of men who have sex with men (MSM) in China, with older MSM experiencing overlapping challenges related to sexual health risks, chronic diseases, and stigma-related barriers to care. Conventional HIV interventions often fail to address these age-specific health priorities. This study evaluated an integrated HIV and chronic disease intervention, informed by the Health Belief Model (HBM), to examine its impact on HIV infection risk among older MSM.</p> Methods <p>A 6-month, single-blind, parallel-group randomized controlled trial was conducted in Tianjin, China. HIV-negative MSM aged ≥ 50 years were randomly allocated to an intervention group (<i>n</i> = 200) or a control group (<i>n</i> = 200). The intervention combined HIV and chronic disease risk education with on-demand integrated testing services, while the control group received routine services. The primary outcome was the HIV Infection Risk Score. Secondary outcomes included condom use at the most recent sexual encounter, participation in group sex, and newly identified HIV and syphilis infections within 6 months. Multivariable linear regression analysis was conducted as an exploratory analysis to identify factors associated with baseline HIV Infection Risk Scores.</p> Results <p>At follow-up, the mean HIV Infection Risk Score was lower in the intervention group than in the control group (mean difference = -1.41, 95% CI: -2.05 to -0.77; <i>P</i> &lt; 0.05). Participants receiving the integrated intervention were less likely to report condomless anal intercourse at the most recent sexual encounter (RR = 0.34, 95% CI: 0.21 to 0.57) and participation in group sex (RR = 0.43, 95% CI: 0.25 to 0.74) within the past 6 months. One new HIV infection was identified in the control group, whereas none occurred in the intervention group. The incidence of syphilis infection did not differ significantly between groups. Sexual role was associated with baseline HIV infection risk, with participants reporting a receptive role exhibiting higher risk scores.</p> Conclusions <p>An integrated HIV and chronic disease intervention was associated with reductions in sexual risk behaviors and overall HIV infection risk among older MSM. Embedding sexual health services within a broader chronic disease management framework may represent a feasible, age-sensitive approach to HIV prevention for ageing sexual minority populations.</p> Trial registration <p>Chinese Clinical Trial Registry, ChiCTR2600117666.Trial registration date: January 27, 2026. Retrospectively registered.</p>