Background: There is limited research evaluating addictions programs for Aboriginal people in urban contexts. Objective: The current project aimed to fill this gap by conducting an evaluation of the Aboriginal Alcohol and Drug Worker Program (AADWP), offered at Friendship Centres in Ontario. Methods: A realist approach was used to evaluate the AADWP. Client-targeted focus groups and staff questionnaires were conducted to develop preliminary theories regarding how, for whom and under what circumstances the program helps or does not help clients. Individual interviews were then conducted with clients and caseworkers to test these theories.Results: Mechanisms through which clients achieved their goals were related to client needs, trust, cultural beliefs, willingness, self-awareness, and self-efficacy. Clients’ goals related to sobriety status, renewing relationships, cultural connection and mental health. Client. Staff and setting characteristics were found to moderate development of mechanisms and outcomes. Results were congruent with existing literature.