Atopic dermatitis (AD) is a common inflammatory skin disease that is characterized by chronic and persisting pruritic and eczematous lesions. There has been no study of work productivity and activity in AD patients in relation to disease severity. The purpose of this study was to examine the impact of disease severity on work productivity and activity impairment (WPAI) in adult AD patients using the Japanese version of the questionnaire. Data were collected from 112 AD patients who visited the Jikei University Hospital. Outcomes as measured by the questionnaire included employment status, total work productivity impairment (TWPI) and total activity impairment (TAI). We investigated the correlation between TWPI or TAI scores and severity scoring of AD (SCORAD) for disease severity and dermatology life quality index (DLQI) for quality of life impairment. Both TWPI and TAI scores were significantly correlated with the SCORAD and DLQI scores (P < 0.001), indicating disease severity is significantly associated with WPAI in Japanese adult AD patients. Further studies are necessary to evaluate the effects of treatments on WPAI for severe AD patients.