Introduction: Low health literacy among girls, women, and people who menstruate is associated with worse reproductive health outcomes. Mobile apps promise tools for improving women’s health literacy, however, there is little information about subscribers’ perceptions of app functionality and its impact on their knowledge and health. Objective: This study aimed to explore knowledge and health improvements related to menstrual cycle and pregnancy, as well as improvements in general health in Flo app users. We also investigated what components of the Flo app were associated with the above mentioned improvements, and evaluated whether those improvements differed based on education level, free or a premium subscription to the app, short or long term use of the app, and frequency of use. Methods: Flo subscribers who had been using the app for no less than 30 days completed an online survey. A total of 2214 of complete survey responses were collected. The survey included demographic questions, questions about motivations guiding usage of the Flo app, to what extent and what components of the app may have helped improve their knowledge and health (i.e., reproductive, sexual, physical, mental health, health behaviours, and communication with healthcare providers).Results: Most study participants reported menstrual cycle (89.0%) and pregnancy (84.6%) knowledge improvements from Flo app use. 62.3% of Flo users reported ‘period predictions’ and 72.2% reported ‘reading and/or watching articles and video sources in the app’ helped them feel the most informed about their cycle and pregnancy health. Higher educated, Flo Premium, frequent, and short term app users reported using the app mainly for getting pregnant and pregnancy tracking. Lower educated and long time users reported using the app to learn more about their body, sexual health, irregular cycles and related conditions, and to avoid pregnancy. Importantly, intended uses of the app for both lower and higher educated users matched areas in which they have gained knowledge and achieved their health goals upon the Flo app use. Flo Premium, frequent, and long term users were more likely to report improvements in knowledge and health in all areas they chose to use the app for and even beyond.Conclusion: There is a need to increase reproductive health literacy in the global female population. This study has shown that the use of the period tracking app, Flo, as self-reported by its users, improved their menstrual cycle and pregnancy knowledge and health. Additionally, more frequent, long-term, and Flo Premium users were more likely to report knowledge and health improvements across multiple health areas. Thus, the use of digital health apps, such as the Flo app, should be considered for integration into healthcare systems to increase women’s health literacy in the wider population.