BACKGROUND: Assisted partner notification (PN) is an effective approach for increasing HIV testing among heterosexual partners. There is sparse evidence on its effect among sexual partners of men who have sex with men (MSM). METHODS: A randomized controlled trial was conducted to compare the effect of assisted PN and passive PN interventions on uptake of HIV testing among male and female sexual partners of newly HIV-diagnosed MSM. In the passive PN group, participants were encouraged to disclose their HIV status and refer and persuade sexual partners to access HIV testing services (HTS). In the assisted PN group, participants were further provided with HIV self-testing kits for sexual partners to take a test at home or allow a community health worker from MSM-serving community-based organization (CBO) to anonymously refer and persuade their sexual partners to access HTS. The primary outcome was the proportion of index cases who had any sexual partner accessing HTS within four months after randomization. This trial is registered with chictr.org.cn, ChiCTR1800017813. FINDINGS: Between August 2017 and January 2019, 187 MSM newly diagnosed with HIV in a large city Shenyang in northern China were enrolled in the study and randomly assigned to either passive PN (n=90) or assisted PN (n=97) study groups. The proportion of index cases who disclosed their HIV status to any sexual partners within three months of randomization was similar between passive PN (57%, 95% confidence interval [CI]: 46-67%) and assisted PN groups (58%, 95% CI: 48-68%). During four months of follow-up, the number of sexual partners named, referred to HTS, tested and testing positive per index case was 3•2, 0•7, 0•2 and 0•03 in the passive PN group, and 4•0, 1•0, 0•5 and 0•10 in the assisted PN group. Thirty-five percent of index cases in the assisted PN group had any sexual partners accessing HIV testing compared to 17% in the passive PN group (P = 0•004); 49% sexual partners who were disclosed by index cases in the assisted PN group had access HTS compared to 28% in the passive PN group (P = 0•007). INTERPRETATION: The assisted PN strategy incorporating HIV self-testing and CBO outreach can increase uptake of HIV testing among sexual partners of MSM who were recently diagnosed with HIV. FUNDING: National Science and Technology Major Project of China, National Natural Science Foundation of China, and Project for Overseas Visiting Research of Liaoning Province.