The opioid epidemic constitutes one of the worst drug crises in the history of U.S. State-level policies, in general, have done little to prevent prescription opioid abuse. A noteworthy exception to other clinical efforts to curb opioid abuse is marijuana. Despite preliminary evidence, many states are hesitant to introduce legislation to expand access to medicinal marijuana or liberalize laws on the recreational use of marijuana, fearing additional research is needed. Utilizing a synthetic control method and annual state-level data from 2006 to 2018, this study examines the effect of recreational marijuana legalization on opioid abuse. The findings strongly indicate marijuana legalization is not a statistically significant factor in reducing opioid abuse in Colorado State. This provides important implications for states designing policies to provide opioid addicts with marijuana substitutes and states hoping to address concerning rises in opioid abuse. Further research needs to be done to develop a robust understanding.