 The study aimed to understand privacy and confidentiality concerns among Malaysian men who have sex with men, MSM, regarding participation in a hypothetical app-based HIV prevention program. The results showed that most participants were willing to participate, but expressed concerns about privacy, confidentiality, data security, and risks and benefits of participating in all stages of the app-based HIV research process. Multivariable logistic regression models identified perceived participation benefits as a positive correlate of willingness to participate, while increased concerns about app-based clinical interaction and e-prescription, and higher degree of perceived risks of participating were negative correlates. The study concluded that mHealth app-based HIV prevention programs are acceptable for future research on Malaysian MSM, but must be safe and secure to ensure widespread public trust and uptake. This article was authored by Roman Shresta, Celia Fisher, Jeffrey A. Wickersham, and others.