Smartphones are ideal for tracking individuals’ behavioral responses. Traditional laboratory-based psychological trials aimed at training cognitive functions face a problem when participants cannot finish their tasks within a scheduled time. In this paper, we developed a self-training system that helps people to enhance their cognitive functions through mental exercises. The system utilizes the advantages of mobile computing and Internet connection. Participants can finish their mental exercises no matter where they are and can send the results back to the data server. Administrators can track all participants’ status on a web-based system. This study investigates in situ the 20-session use of a mobile application. The results reveal that the users significantly enhanced their level of executive functions. The dropout rate was very small. This application, which uses a cloud data server, makes it more efficient and cost-effective in conducting psychological training programs. The proposed system provides a basic smartphone-based system for psychological trials and can be further improved by combining other techniques such as speech recognition and data-mining techniques.