Background <p>Despite extensive research on the broader effects of recreational cannabis legalization (RCL), limited attention has been given to its impact on cannabis use disorder (CUD) treatment outcomes. This study addresses this gap by analyzing CUD treatment outcomes, including 90-day treatment retention and successful discharge.</p> Methods <p>Data were collected from a dataset of all publicly funded cannabis use disorder treatment delivered in California between January 2010 and December 2021 (<i>n</i> = 192,580). RCL’s impacts on CUD treatment outcomes was estimated using an individual-level pre-post time series model, including individual and county-level characteristics via logistic regression.</p> Results <p>California’s RCL was associated with a significant decrease in the probability of 90-day treatment retention and also of successful discharge from treatment for patients with a CUD. RCL was also associated with a decrease in the probability of 90-day CUD treatment retention for adults ages 21 + and White Non-Hispanics, and a decrease in the probability of successful discharge for White Non-Hispanics, and an increase in the probability of successful discharge for males and adults ages 21+. We find no association between RCL and treatment retention or successful discharge for Black Non-Hispanic or Hispanic patients.</p> Conclusions <p>The implementation of California’s RCL was associated with a decline in CUD treatment outcomes. The findings underscore the need for ongoing evaluation of cannabis legalization’s effects on public health to inform policy and practice in the context of evolving cannabis regulations.</p>