Atopic dermatitis (AD) is associated with itch, pain, and sleep disturbance, all of which may contribute toward cognitive dysfunction.To determine the relationship of AD severity and cognitive function in adults.We performed a prospective dermatology practice-based study using questionnaires and evaluation by a dermatologist (n=386). Cognitive function was assessed using Patient-Reported Outcomes Measurement Information System (PROMIS®) Cognitive Function 8-item short-form.At baseline, 118 (58.1%) patients reported ≥1 symptom of cognitive dysfunction in the past 4-weeks, with 29 (14.3%) having mild, 11 (5.4%) moderate and 4 (2.0%) severe PROMIS Cognitive Function T-scores. In propensity score weighted regression models, PROMIS Cognitive Function T-scores were inversely associated with patient-reported global AD severity, POEM, NRS worst-itch and skin-pain, SCORAD-sleep, POEM-sleep, EASI and SCORAD, with stepwise decreases of cognitive function with worsening AD severity. At all AD severity levels, cognitive dysfunction was associated with increased DLQI and ItchyQOL scores. Changes from baseline in PROMIS Cognitive Function T-scores were weakly-moderately inversely correlated with changes from baseline in multiple AD outcomes.Single-center study without non-AD controls.Cognitive dysfunction is associated with AD severity. Cognitive function may be an important endpoint for monitoring treatment response in AD.