mHealth refers to the use of mobile technologies in the provision of health care and is an expanding field within psychotherapy research. Mobile technologies have the capacity to greatly enhance patient access, uptake, and engagement in psychological treatment. The purpose of the present article is to define mHealth within clinical psychology, provide a review and discussion of the functionality of mHealth devices, current trends within the field of psychological mHealth, the challenges faced by researchers and clinicians in this field, and examine directions for future research. The main areas of research identified included the use of SMS technologies, ecological momentary assessment, online and software application-based interventions and the recent integration of sensor and data mining technologies. Much of the research to date is lacking in methodological rigor, and reliance on standard research designs often used in other areas of psychological research may constrain development of interventions. Research indicates that consumers want to engage in mHealth interventions, although only a limited number of empirically supported options currently exist. Future research incorporating innovative trial designs is required to meet consumer demand and provide users with evidence-based treatment options.