Involuntary civil commitment (ICC) is a legal process by which people are compulsorily admitted to substance use treatment. This study explored views about and promotion of ICC procedures for substance use disorders among public health-public safety post-overdose outreach programs and their outreach team members in Massachusetts, USA. In this mixed-methods study, survey data were collected from post-overdose outreach programs in 2019, and semi-structured interviews were conducted with outreach team members in 2019 and 2020. Massachusetts, USA. We received 138 survey responses and conducted 38 interviews with post-overdose outreach team members (law enforcement officers, recovery coaches, social workers and harm reductionists) who were majority male (57%) and white (66%). We used the survey instrument to categorize programs as more (discussed ICC at 50% or more of outreach encounters) or less ICC focused (discussed ICC at less than 50% of outreach encounters) and to identify program characteristics that corresponded with each categorization. Semi-structured interviews explored staff perceptions of ICC effectiveness. Among 138 programs, 36% (n = 50) discussed ICC at 50% or more of outreach encounters. Discussing ICC at a majority of visits was positively associated with abstinence-only program philosophies (36% v. 6%, P < 0.001) and collaborating with drug courts (60% v. 30%, P < 0.001), but negatively associated with naloxone distribution (48% v. 75%, P < 0.001) and referring to syringe service programs (26% v. 65%, P < 0.001). Qualitative interviews identified three themes: 1) some programs viewed ICC as a first line tool to engage overdose survivors in treatment; 2) other programs considered ICC a last resort, skeptical of its benefits and concerned about potential harms; 3) families commonly initiated discussions about ICC, reportedly out of desperation. Promotion of involuntary civil commitment (ICC) appears to vary widely across post-overdose outreach programs in Massachusetts, USA, with approaches ranging from seeing it as a first step to treatment to being a tool of last resort. Demand for ICC among family members may relate to inadequate access to voluntary treatment. Family interest in ICC appears to be driven by inadequate availability of treatment and other services. ICC at post-overdose outreach visits should be limited, if used at all.