Objective: This article aimed to critically review the literature on online counseling.Method: Database and hand--searches were made using search terms and eligibility criteria, yielding a total of 123 studies.Results: The review begins with what characterizes online counseling. Outcome and process research in online counseling is reviewed. Features and cyberbehaviors of online counseling such as anonymity and disinhibition, convenience, time--delay, the loss of social signaling, and writing behavior in cyberspace are discussed. Ethical behavior, professional training, client suitability, and clients' and therapists' attitudes and experiences of online counseling are reviewed.Conclusion: A growing body of knowledge to date is positive in showing that online counseling can have a similar impact and is capable of replicating the facilitative conditions as face--to--face encounters. A need remains for stronger empirical evidence to establish efficacy and effectiveness and to understand better the unique mediating and facilitative variables.The field of cyberpsychology involves the study of human experiences (cognitive, emotional, and behavioral) that are related to or effected by developing technologies, in other words the psychological study of human--technology interaction (Richards & Viganó, 2012). One area of cyberpsychology is online counseling, also referred to as e--therapy, e--counseling, or cybertherapy. While the very nature and definition of online counseling have been debated, we will use the one employed by Richards and Viganó (2012), defining online counseling as the delivery of therapeutic interventions in cyberspace where the communication between a trained professional counselor and client(s) is facilitated using computer--mediated communication (CMC) technologies, provided as a stand--alone service or as an adjunct to other therapeutic interventions.Alongside technological developments online counseling has grown in the past 15 or so years. Researchers in online counseling have been considering the potential effectiveness of online counseling and whether it is possible to establish a therapeutic relationship in cyberspace. Research studies have focused on establishing its potential benefits and challenges, client suitability for online counseling, therapists' and clients' attitudes and experiences of online counseling, and professional training for working online with clients. Additionally, its very nature and definition as a therapeutic intervention has been debated. Researchers have been exploring newly observed phenomena that form part of understanding the psychology of online counseling behavior. Areas of interest include the effects of apparent anonymity and distance, disinhibition, identity and impression management, writing and emotional expression in cyberspace, and ethical behavior in cyberspace.While other reviews of online counseling have been written, notably, the special issue from the Journal of Clinical Psychology, 2004, and the volume from The Counseling Psychologist, 2005,...