Computer scientists contend that understanding human computer interaction (HCI) is an important factor in developing successful computer user experiences. Mental health professionals across a range of disciplines are increasingly developing and implementing Internet-based treatments for people with a variety of mental health conditions. Many therapeutic and economic benefits are associated with technology-enabled treatments for a range of mental health disorders. Despite this, the role of HCI and associated design elements remains poorly understood in regard to the impact on patient safety, effectiveness, and to adherence of treatment for computer users who engage with e-mental health interventions. An integrative literature review was conducted to investigate how adequately HCI and user-centred design is incorporated in the development of e-mental health interventions for depression and anxiety, and subsequently reported in literature to inform evidence-based practice. The PRISMA model was used to locate, select, and include 30 relevant articles. The main finding of this review is that Internet-based e-mental health interventions are routinely implemented without sufficiently describing the relevant HCI design features applied. This is a limitation that in turn jeopardizes the assessment validity of e-mental interventions generally, leaving those who administer the interventions with incomplete evidence to support the safe, reliable, dependable, credible, and trustworthy implementation of the interventions. The recommendation arising from this review is that human computer interaction should be carefully considered when mental health nurses and other practitioners adopt e-mental health interventions for therapeutic purposes to assure the quality and safety of e-mental health interventions on offer to patients.