In the United States, law enforcement officers serve as first responders to most health crises, allowing them to connect many more individuals to treatment services than other government actors, a fact that has come into increasing focus due to the opioid epidemic. In response, police departments across the country have begun to divert individuals that possess narcotics away from arrest and towards treatment and recovery. Evidence on whether these programs are able to engender meaningful change—initially by increasing participation in substance use treatment, and eventually by reducing the likelihood of continued drug use and criminal justice involvement—remains limited. This paper aims to shed light on the potential of these programs by exploiting the eligibility criteria for and staggered rollout of narcotics arrest diversion in Chicago between 2018 and 2020 using a difference-in-difference-in-differences framework. We find that the program reaches individuals with medically diagnosed substance use disorders, increases connections with substance use treatment, and reduces subsequent arrests. We conclude that Chicago’s drug diversion program is able to simultaneously reduce the reach of the criminal justice system, expand the number of individuals with substance use disorders connected with treatment, and improve public safety.