Objective: To examine the associations between medical marijuana policies and opioid‐related hospitalizations and emergency department visits. DataSources: We utilized quarterly rates of hospital discharge data from the Healthcare Cost and Utilization Project’s (HCUP) Fast Stats Database from 2005 to 2016 along with state‐level sociodemographic data from US Census Bureau and Bureau of Labor Statistics and opioid‐related state health policy data from publicly available sources for the analysis. Study Design: Analyses were carried out using a difference‐in‐differences regression approach. We estimate heterogeneous effects of medical marijuana policies such as initial policy, presence of active dispensary, and home cultivation on opioid‐related hospitalizations and emergency department visits related to opioids. Data Collection/Extraction Methods:Publicly available secondary data were collected, linked, and analyzed. Observations with missing values for explanatory variables were excluded from the analysis. Principal Findings: Regression results indicate that type of medical marijuana policy has varying effects on opioid‐related hospitalizations and emergency department visits. States that allow home cultivation of medical marijuana experienced significant positive associations with opioid‐related hospitalizations and emergency department visits, while no effect was observed with medical marijuana dispensaries. Moreover, recreational marijuana policies were positively associated with opioid‐related hospitalizations. Conclusions: The findings indicate that the effects of medical marijuana policies on opioid‐related hospitalizations and emergency department visits vary depending on the type of medical marijuana policy. Our findings indicate that the implementation of home cultivation of marijuana is positively associated with hospitalizations and emergency department visits related to opioids, suggesting that easier access to marijuana among opioid users may result in adverse health conditions that need treatment.