BACKGROUND: Dating applications are a popular platform to meet new people. At the same time, they have been associated with risks such as unsafe sexual behavior and privacy concerns in young adults. This paper presents a study protocol of a cluster randomized controlled trial (RCT) to evaluate the effectiveness of a peer-led web-based intervention to promote its safe usage in young adults. METHODS: The study design is an open-labeled cluster RCT with an intervention and a placebo control arm. The intervention group will receive a web-based intervention developed through focus group discussions, a crowdsourcing contest, and a Peer-Vetted Creative Production (PVCP) workshop. The control group will receive a web-based resource on health and exercise. We aim to recruit approximately 338 young adults aged 17-27 years from three tertiary educational institutions in Hong Kong with the class as the cluster unit. Based on the Information, Motivation, and Behavioral Skills (IMB) model, the primary outcome of this study is self-efficacy in using dating applications measured by the General Self Efficacy Scale. Secondary outcomes include change in risk perception measured by the Risk Propensity Scale and a Risk Assessment Tool. Questionnaires will be administered before the intervention, after the intervention, and at one-month follow-up. Intention-to-treat analysis and multilevel regression modeling will be used to evaluate differences in outcomes between groups and the factors affecting these outcomes, respectively. DISCUSSION: Dating application usage presents opportunities as well as challenges to young adults meeting new friends. Innovative and relatable interventions are needed to promote the safe usage of dating applications to this population. Practical knowledge gained from the development process may be helpful for future intervention utilizing the peer-led approach. If effective, the intervention will be disseminated to non-governmental organizations and educational institutions to be used as a teaching resource. TRIAL REGISTRATION: ClinicalTrials.gov, NCT03685643 . Registered on 26 September 2018. University of Hong Kong Clinical Trials Registry, HKUCTR-2512.