This study is a natural quasi-experiment to examine the development of religiosity and virtues among Muslim American adolescents before, during, and after Ramadan using online surveys and experience sampling surveys. We wanted to examine whether Ramadan heightens Muslim American adolescents’ connectedness to Allah, self-control, patience, compassion, gratitude, shame and guilt. We used experience sampling surveys prior to, during, and after Ramadan to capture daily nuances in adolescents’ religiosity and underlying processes that foster their daily virtues. Rather than capturing behavior or feelings retroactively over a vast period of time (e.g., “Think about how you have felt over the past year”), ESM methods allow us to capture behaviors and feelings during normal daily life, as they are happening in real time – what’s called “situational.” This method also allows us to understand how people change compared to themselves, rather than to the rest of the study sample. This study is the first to provide systematic quantitative investigation regarding the effects of Ramadan on the within-person changes in daily virtues of Muslim American adolescents before, during, and after Ramadan.