Background Excess mortality has been reported for adults with atopic dermatitis (AD) and asthma. Objective To assess the mortality rate in adults with concomitant AD and asthma. Methods Adults with hospital-diagnosed AD were matched (1:4) with non-AD individuals from the background population. Results The study cohort comprised 8,095 adults with AD (of which 1,201 (14.8%) had concomitant asthma) and 32,380 reference individuals without AD from the background population (of which 878 (2.7%) had asthma). A total of 1,057, 330, 55 and 99 deaths were observed among subjects with neither AD nor asthma, AD only, asthma only, and subjects with concomitant AD and asthma, respectively. The mortality rate per 1,000 person-years was 4.75 (95% CI 4.47-5.05) for subjects with neither AD nor asthma, 7.17 (95% CI 5.92-10.05) for asthma only, 7.09 (95% CI 6.37-7.90) for AD only and 10.87 (95% CI 8.92-13.23) for concomitant AD and asthma. Risk for all-cause mortality was increased in subjects with concomitant AD and asthma compared to asthma only (HR 1.52, 95% CI 1.07-2.15) and neither AD nor asthma (HR 2.27, 95% CI 1.83-2.81) but not compared to subjects with AD only (HR 1.10, 95% CI 0.87-1.39). However, compared to AD only subjects with AD and asthma had increased risk of death due to pulmonary disease (HR 1.81, 95% CI 1.04-3.15). Conclusion Adults with AD, asthma or both conditions have increased risk of death, and further concomitant AD and asthma have increased risk of death compared with asthma alone.