The aim of this review was to explore the barriers and mechanisms that influence how people are referred to, and supported within, formal gambling harm treatment services. A total of 39 studies were included in the review. Ten core themes were identified and organized according to the Antecedents–Decision–Outcomes (ADO) framework. The framing of responsibility is a cross-cutting factor that shapes the recognition of and response to gambling harm. The results point to a need for better integration of referral and treatment pathways for gambling harm.