The purpose of this work is to obtain a set of best practices for the design of mental health smartphone applications (MHSAs) for an adolescent user base. The authors carried out a systematic literature review combined with a bibliographic coupling analysis to identify relevant literature, and then a thematic analysis of the literature to identify core principles. These efforts led to a framework of nine general principles for the creation and design of MHSAs. The nine core principles identified were: Using evidence-based treatments, encouraging intrinsic motivation in users, using extrinsic behavior triggers, providing professional support, enabling social support, engaging users during the development process, using user-centered design principles, including a parental mode, and protecting patients’ privacy.