INTRODUCTION: Male partner HIV testing and engagement in antenatal care (ANC) is associated with improved clinical outcomes for men, pregnant women and infants. However, testing rates remain low among male partners of pregnant women receiving ANC in Africa. We evaluated the impact of male peer outreach to increase HIV testing among partners of pregnant women in Uganda. METHODS: We conducted a randomized trial in Kampala, Uganda, enrolling an equal number of pregnant women with and without HIV from public ANC clinics who were randomized 1:1 to intervention or standard-of-care (SOC) with delayed intervention after 1 month. (ClinicalTrials.gov ID, NCT05388084). The intervention consisted of male peer counsellors calling male partners of consenting pregnant women and inviting them to test for HIV. In the SOC, pregnant women received an invitation letter to deliver to their partners for fast-track HIV testing, per national guidelines. We conducted an intention-to-treat analysis using modified Poisson regression, comparing the proportion of male partners tested for HIV by month 1 across arms overall and by female's HIV status. A secondary analysis compared the proportion tested for HIV by 3 months after both arms received the intervention. RESULTS: Between May 2022 and March 2023, we enrolled 150 pregnant women (76 in intervention, 74 in SOC). At 1 month, 18% more males in the intervention arm tested for HIV compared to SOC (32% vs. 14%; risk difference [RD] = 0.18; 95% confidence interval [CI]: 0.05-0.31). This association remained significant after stratifying by female HIV status. HIV testing was 22% higher among male partners of HIV-negative women in the intervention arm compared to SOC (46% vs. 24%; RD = 0.22; 95% CI: 0.004-0.430) and 15% higher among partners of pregnant women with HIV (18% vs. 3%; RD = 0.15; 95% CI: 0.02-0.28). At 3 months, 50% (38/76) of male partners tested in the intervention versus 35% (26/74) in the SOC/delayed intervention (RD = 0.15; 95% CI: -0.01 to 0.31). CONCLUSIONS: Male peer outreach is a promising intervention to increase knowledge of HIV status among partners of pregnant women. Additional support is needed to increase HIV testing among partners of women with HIV.