Objective To propose some key steps to facilitate the process of creating mental health smartphone applications (apps). Methods Brief presentation of the potential interest of apps and proposition of key steps for the creation of apps. The paper is based on a narrative review, a testimonial experience and some expert works. Results Apps have ubiquitous features that are particularly appealing for the mental health field. Potentially connected to multiple technologies, mobile and available at all times, they allow great design flexibility. In order to increase the chances of effectiveness and good dissemination of a given app, 9 principles could usefully guide the design of apps, in particular a good integration of end users around well-defined target objectives during the entire process of creating such tools. Conclusion The proposed key steps could facilitate the process of creating mental health apps.