As attempts to decriminalise the personal possession of drugs have foundered in North America over concerns about its negative effects on crime and public order, Portugal's 2001 decriminalisation strategy remains widely regarded as the most successful reform to date. Despite this success, there is little research about the experience of Portugal's national police as central actors in the initiative. Addressing this gap, this study investigated Portuguese Police and Public Safety experiences with decriminalisation through qualitative interviews with 19 participants, principally consisting of veteran police executives and national police and health policymakers who had direct roles in implementing and discharging the nation's drug policy, as well as street-level patrol and narcotics officers. Participants explained police practices within Portugal's drug decriminalisation policy that made it compatible with maintaining public safety and order, contributing to the feasibility and acceptability, among police, of a drug control strategy associated with nationwide reductions in fatal overdose and infectious disease. They stressed: the deliberate manner in which decriminalisation was planned and implemented; how the shift prioritised public health, relying on police as conduits to health-related interventions that also reduced the criminal activity motivated by substance use disorder; the police role referring otherwise difficult-to-reach people with addiction treatment and social services; the provisions through which police could effectively address disruptive public drug use and pursue narcotics trafficking. Decriminalisation shifted the police role in Portuguese society, resulting in the gradual evolution of police culture towards its acceptance. Policymakers can use Portugal as a case study of successful innovation.