ImportanceIn the US, cannabis use has nearly doubled during the past decade, in part because states have implemented recreational cannabis laws (RCLs). However, it is unclear how legalization of adult-use cannabis may affect alcohol consumption.ObjectiveTo estimate the association between implementation of state RCLs and alcohol use among adults in the US.Design, Settings, and ParticipantsThis was a cross-sectional study of 4.2 million individuals who responded to the Behavioral Risk Factor Surveillance System in 2010 to 2019. A difference-in-differences approach with demographic and policy controls was used to estimate the association between RCLs and alcohol use, overall and by age, sex, race and ethnicity, and educational level. Data analyses were performed from June 2021 to March 2022.ExposuresStates with RCLs, as reported by the RAND−University of Southern California Schaeffer Opioid Policy Tools and Information Center.Main Outcomes and MeasuresPast-month alcohol use, binge drinking, and heavy drinking.ResultsOf 4.2 million respondents (median age group, 50-64 years; 2 476 984 [51.7%] women; 2 978 467 [58.3%] non-Hispanic White individuals) in 2010 through 2019, 321 921 individuals lived in state-years with recreational cannabis laws. Recreational cannabis laws were associated with a 0.9 percentage point (95% CI, 0.1-1.7; P = .02) increase in any alcohol drinking but were not significantly associated with binge or heavy drinking. Increases in any alcohol use were primarily among younger adults (18-24 years) and men, as well as among non-Hispanic White respondents and those without any college education. A 1.4 percentage point increase (95% CI, 0.4-2.3; P = .006) in binge drinking was also observed among men, although this association diminished over time.Conclusions and RelevanceThis cross-sectional study and difference-in-differences analysis found that recreational cannabis laws in the US may be associated with increased alcohol use, primarily among younger adults and men.