With the coronavirus disease (COVID-19) outbreak, social distancing and constant vigilance against infection have become the "new norm". Not surprisingly, multiple mental health problems arising during the pandemic are of increasing global concern. Telemedicine or mHealth is being more highlighted than ever during this major ongoing global health and economic crisis. This review aims to explore current mHealth approaches introduced in the scientific literature for mental illnesses including depressive disorders, anxiety disorders, obsessive-compulsive and related disorders, trauma-and stressor-related disorders, bipolar and related disorders, schizophrenia spectrum and other psychotic disorders, eating disorders, sleep-wake disorders, and substance-related disorders. Implications for the choice of use, evaluation, and further development of mHealth interventions are also discussed to harness mHealth as an alternative or augment to traditional mental health services.