BACKGROUND: Preexposure prophylaxis (PrEP) remains one of the most efficacious interventions for preventing HIV, but its effectiveness is often limited by poor persistence. Although regional efforts have primarily focused on young women and men who have sex with men, heterosexual men in East and Southern Africa represent a crucial group to engage and retain in PrEP care-both to improve health outcomes for men and to interrupt HIV transmission chains. Men seeking sexually transmitted infection (STI) services are particularly vulnerable to HIV acquisition, yet only a few interventions have tested strategies for engaging and retaining these men in PrEP services. Systems navigation, which addresses barriers to health care access and enhances comfort in clinical settings, may offer a promising approach to improving persistent PrEP use among heterosexual men. OBJECTIVE: This study will assess the effect of a peer-delivered systems navigator-facilitated HIV prevention package on PrEP persistence at 26 weeks among heterosexual men seeking STI clinical services in Lilongwe, Malawi. It will also evaluate the acceptability of the intervention and barriers to implementation among key stakeholders. Insights will inform the feasibility of a future randomized controlled trial. METHODS: In this single-site pilot type I effectiveness-implementation hybrid randomized controlled trial, 200 heterosexual men seeking STI services and initiated on PrEP in Lilongwe, Malawi, will be randomized (1:2) to standard-of-care PrEP services or systems navigator-assisted PrEP care (intervention). Participants will be followed every 13 weeks for at least 26 and up to 52 weeks. PrEP use and engagement in care will be assessed through medical record review and intraerythrocytic tenofovir diphosphate measurement, using objective biomedical analyses via dried blood spot. Primary effectiveness and implementation outcomes include 26-week PrEP persistence (adapted to accommodate daily oral, event-driven oral, or injectable PrEP) and acceptability, respectively. Additional implementation outcomes include feasibility and cost. Exploratory objectives characterize preferences for PrEP modalities, perceived and experienced stigma, and the influence of gender norms on PrEP persistence. All clinical services, including the provision of PrEP and PrEP safety monitoring, are being conducted by the Malawi Ministry of Health. RESULTS: HPTN (HIV Prevention Trials Network) 112 was funded in November 2023. Study recruitment began in April 2024 and closed in November 2024. As of February 3, 2025, the study has enrolled 199 participants, with follow-up expected through June 2025. No interim analyses were planned; data analysis for primary end points is expected in the summer of 2025. CONCLUSIONS: Improving PrEP use outcomes among heterosexual men in East and Southern Africa is critical to interrupting HIV transmission. This study offers unique insights into a low-resource, potentially scalable intervention, focusing on a group of men at particularly high risk of HIV acquisition-those with recent STIs. The hybrid RCT design addresses clinically relevant effectiveness questions and explores key determinants that will inform future multisite implementation trials. TRIAL REGISTRATION: ClinicalTrials.gov NCT06200545; https://clinicaltrials.gov/study/NCT06200545. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/72981.