The ubiquity of mobile devices and access to the internet has changed our daily life and, in some cases, promoted and facilitated social and sexual interrelationships. There are many applications of technology and campaigns promoting healthy behaviors and prevention of sexually transmitted infections. Can we develop a strategy for the same purpose using mobile devices, based on the theory of attitude change? We developed an app and tested it with 105 undergraduate students, where they had to actively think in favor of condom use with a high amount of elaboration, leading to attitudes and behavioral intention (BI) in concordance with contemporary theories about attitudes and behavioral change. PROCESS macro models were used to analyze potential mediations. Results show a significant correlation between thoughts and attitudes, and attitudes partially mediated the association between thoughts and condom use. Individuals with positive thoughts tended to positively correlate their thoughts with their attitudes, and, consequently, these attitudes with their BI. In this study, we showed that (1) it was possible to develop and test an app based on the elaboration likelihood model (ELM); (2) consistent with previous studies, attitudes partially mediated the association between thoughts and condom use (BI) in a mobile environment; and (3) applications of this strategy can be used to build new approaches for prevention in health care.