Background The health, social, and economic costs of sexually transmitted infections (STIs) represent a major public health concern. Young people are considered one of the groups most at risk for acquiring and transmitting STIs. Correct and consistent condom use has been shown to be the most effective method for reducing STIs; however, condoms are often not used properly. Evidence shows that brief behavior change interventions that focus on skills, communication, and motivation to acquire safe sex practices should be adopted into routine care to reduce STIs. Funding for sexual health services in England has declined dramatically, so novel ways of reducing clinic attendance are being sought. The home-based intervention strategy (HIS-UK) to promote condom use among young men has shown promise in feasibility and pilot studies by demonstrating high acceptability of the intervention in participant and health professional feedback, including aiding men to find condoms they like and feel more confident when using condoms. Objective The aim of this study is to determine the effectiveness and cost-effectiveness of HIS-UK when compared to usual condom distribution care among young men. Methods The 3 trial arms consisting of “e-HIS” (HIS-UK delivered digitally), “ProHIS” (HIS-UK delivered face-to-face), and control condition (usual National Health Service [NHS] care) will be compared against the following 3 primary outcomes: the extent to which correct and consistent condom use is increased; improvement of condom use experiences (pleasure as well as fit and feel); and decrease in chlamydia test positivity. Eligibility criteria include men aged 16-25 years at risk of STIs through reporting of condom use errors (ie, breakage or slippage) or condomless penile-vaginal or penile-anal intercourse with casual or new sexual partners during the previous 3 months. Prospective participants will be recruited through targeted advertisements and an opportunistic direct approach at selected sexual health and genitourinary medicine services and university-associated health centers and general practitioner practices. Community and educational establishments will be used to further advertise the study and signpost men to recruitment sites. Participants will be randomly allocated to 1 of 3 trial arms. A repeated measures design will assess the parallel arms with baseline and 12 monthly follow-up questionnaires after intervention and 3 chlamydia screening points (baseline, 6, and 12 months). Results Recruitment commenced in March 2020. Due to the COVID-19 pandemic, the study was halted and has since reopened for recruitment in Summer 2021. A 30-month recruitment period is planned. Conclusions If effective and cost-effective, HIS-UK can be scaled up into routine NHS usual care to reduce both STI transmission in young people and pressure on NHS resources. This intervention may further encourage sexual health services to adopt digital technologies, allowing for them to become more widely available to young people while decreasing health inequalities and fear of stigmatization. Trial Registration ISRCTN Registry ISRCTN11400820; https://www.isrctn.com/ISRCTN11400820