We investigate the impact of supportive housing (Housing First, or HF) programs on public service utilization of people experiencing homelessness in Calgary, Alberta. We use data on clients between 2012 and 2016, and, using a pre–post design, we assess the interaction of each client with the health and justice systems. We estimate the savings for $1 spent on HF to be between $1.17 and $2.84. There are potential estimation biases, but our estimates are broadly consistent with evidence from randomized controlled trials. Our somewhat higher estimated returns may be attributed to the practice of program delivery and effectiveness of the triage system.