Abstract Background In a cohort of migrants in Denmark, we compared somatic disease incidence among migrants diagnosed with posttraumatic stress disorder (PTSD) and depression with migrants without a diagnosed psychiatric disorder. Methods The study builds on a unique cohort of migrants who obtained residence permit in Denmark from 1993 to 2010 ( N = 92,104). The association with somatic disease was explored via register linkage. We used Poisson regression to model incidence rate ratios (IRR) adjusted for age, sex, income and region of origin. The Danish Data Protection Agency granted authorisation for the implementation of the project (No 2012-41-0065). Results Our results showed that migrants diagnosed with PTSD and depression had significantly higher rates of somatic diseases compared with migrants without diagnosed psychiatric disorders – especially, infectious disease (IRR, 1.89; 95% CI, 1.45–2.48; p