This paper evaluates the causal effect of drug decriminalization on unintentional drug overdose deaths in a context with relatively poor access to drug treatment services. Using the synthetic control method, I find that when Oregon decriminalized small amounts of drugs in February 2021, it caused 182 additional unintentional drug overdose deaths to occur in Oregon in 2021. This represents a 23% increase over the number of unintentional drug overdose deaths predicted if Oregon had not decriminalized drugs.