Objective We aimed to investigate the annual incidence and direct medical cost of adjustment disorder in general population using the National Health Insurance Service Database (NHID) in Korea. Methods To examine the incidence, we selected patients who had at least one medical claim for adjustment disorder and had not been diagnosed in the previous 365 days, from 2010 to 2017. Results The number of newly diagnosed cases of adjustment disorder from 2011 to 2017 were total 101,922. Annual incidence of adjustment disorder was ranged from 22.0 to 36.8 per 100,000 persons. The incidence of adjustment disorder was found more in female and highest among 70-79 years of age group and medical aid beneficiaries group. Annual prevalence of adjustment disorder was in the range from 95.4 to 116.4 per 100,000 persons. Estimated annual medical cost per person of adjustment disorder was ranged from 162 to 231.4 US dollars. Conclusion From 2011 to 2017, the annual incidence and direct medical cost of adjustment disorder in Korea were increased. Proper information on adjustment disorder will not only allows us to accumulate more knowledge but also lead to more appropriate therapeutic interventions.