Background: "Befriending" involves pairing a volunteer with a person with a mental illness in the community to spend social time together. The term can have very different connotations.Aims: To review how "befriending" was used in mental health care.Method: A systematic review with a narrative synthesis was used to explore how befriending is conceptualised and practiced. We extracted descriptions of "befriending" from efficacy studies, befriending manuals, and reports from the gray literature and explored the practical implications of the different concepts of "befriending".Results: The lay understanding of the phrase "to befriend" is "to be a friend to". This contrasts to codes of practice used by befriending organisations, which describes a relationship distinct from friendship. The literature (12 relevant papers total) suggests a spectrum of practices; at one end is a relationship that is professional or therapeutic in nature, while at the other end, the relationship is conceptualised as much closer to a naturally occurring friendship.Conclusion: The different concepts determine distinct practices, which may lead to confusion when the term befriending is used. The term "befriending", may be understood to concern friendship, which may be inappropriate where the organisation offers a professional style relationship.