BackgroundControl of alcohol licensing at local government level is a key component of alcohol policy in England. There is, however, inconsistent and weak evidence of public health impact while inevitably there is variation in local delivery. We designed a natural experiment and used Bayesian structural time-series to estimate the impact of new local alcohol licensing policies on population health and crime. MethodsHome Office licensing data (2007–12) were used to identify exposed areas (local areas where both a cumulative impact zone [CIZ] and increased licensing enforcement intensity, defined as refusal of new licensing applications, were introduced in 2009 and 2010), and unexposed areas (without evidence of CIZ or refusal of alcohol licences), chosen to maximise contrast. Outcomes were publicly available data from Public Health England on alcohol-related directly age-standardised hospital admissions and from the Office of National Statistics on alcohol-related violent crimes during 2009–15. Bayesian structural time-series incorporating a steady state, a regression, and a seasonal component were used to create synthetic control areas from weighted (based on inclusion probabilities [non-Null effects in Markov Chain Monte Carlo sampling]) time trends in unexposed areas. These described the trends in exposed areas if no exposure had occurred. Intervention effects were calculated from differences between observed 2011–15 trends and modelled trends in synthetic control areas. Posterior effects across all exposed areas were calculated with random-effects meta-analysis and expressed as point-estimates and 95% credible intervals (CI). Sensitivity analyses were conducted using randomly selected control areas from all unexposed areas. FindingsFive local exposed areas and 86 unexposed areas were identified with generally downward trends in outcomes. Compared with postintervention trends in the synthetic controls, hospital admissions and violent crimes in the exposed areas had an additional −6% (95% CI −13 to 0) and −4% (−14 to 5) reduction over 2011–15 compared with expected trends. No evidence of additional reductions was observed in unexposed areas. The findings were insensitive to choices of Bayesian priors. InterpretationModerate reductions in violent crime and modest reductions in alcohol-related hospital admissions were associated with introduction of alcohol licensing policies. An important limitation of the methodology is that the inferences made rely on the assumption that the association between the control and the intervention areas before the intervention remains similar in the postintervention period. Nonetheless, this novel methodology is promising for use in other natural experiments in public health. FundingNational Institute for Health Research (NIHR) School for Public Health Research.