Many privately insured adults with drug use disorders in the United States do not have health care coverage for drug use treatment. The Affordable Care Act sought to redress this gap by including substance use treatments as essential health benefits under new plans offered. This study used data from 11,732 privately insured adult participants of the 2005-2018 National Survey on Drug Use and Health with drug use disorders to examine trends in drug use treatment coverage and the association of coverage with receiving treatment. 37.6% of the participants with drug use disorders did not know whether their plan covered drug use treatment, with little change over time. Among those who knew, coverage increased modestly between the 2005-2013 and 2014-2018 periods (73.5% vs. 77.5%, respectively, p = .015). Coverage was associated with receiving drug use treatment (adjusted odds ratio = 2.09, 95% confidence interval = 1.61-2.72, p < .001). However, even among participants with coverage, only 13.4% received treatment. Broader coverage of drug use treatment could potentially improve treatment rates.