Rationale: Estimating the annual incidence and prevalence of nontuberculous mycobacterial (NTM) lung disease may assist in improving understanding of the public health and economic impacts of this disease and its treatment.Objective: To estimate the yearly incidence and prevalence of administrative claims–based NTM lung disease between 2008 and 2015 in a U.S. managed care claims database.Methods: We used a national managed care claims database (Optum Clinformatics Data Mart) representing a geographically diverse population of approximately 27 million members annually. All medical claims from January 1, 2007, to June 30, 2016, were scanned for diagnosis codes for NTM lung disease (International Classification of Diseases, Ninth Revision, Clinical Modification [ICD-9-CM] code 031.0 or ICD-10-CM code A31.0). We defined a case of NTM lung disease as having at least two medical claims with a code of 031.0 or A31.0 that were dated at least 30 days apart. Annual incidence and prevalence were estimated for each calendar year from 2008 to 2015.Results: From 2008 to 2015, the annual incidence of NTM lung disease increased from 3.13 (95% confidence interval [CI], 2.88–3.40) to 4.73 (95% CI, 4.43–5.05) per 100,000 person-years, and the annual prevalence increased from 6.78 (95% CI, 6.45–7.14) to 11.70 (95% CI, 11.26–12.16) per 100,000 persons. The average annual changes in incidence and prevalence were +5.2% (95% CI, 4.0–6.4%; P < 0.01) and +7.5% (95% CI, 6.7–8.2%; P < 0.01), respectively. For women, the annual incidence increased from 4.16 (95% CI, 3.76–4.60) to 6.69 (95% CI, 6.19–7.22) per 100,000 person-years, and the annual prevalence increased from 9.63 (95% CI, 9.08–10.22) to 16.78 (95% CI, 16.04–17.55) per 100,000 persons. For individuals aged 65 years or older, the annual incidence increased from 12.70 (95% CI, 11.46–14.07) to 18.37 (95% CI, 16.98–19.87) per 100,000 person-years, and the annual prevalence increased from 30.27 (95% CI, 28.41–32.24) to 47.48 (95% CI, 45.37–49.67) per 100,000 persons. The incidence and prevalence of NTM lung disease increased in most U.S. states and overall at the national level.Conclusions: The incidence and prevalence of NTM lung disease appears to be increasing in the United States, particularly among women and older age groups.