Background There are a few case reports in literature that isotretinoin treatment may alter sleep architecture. Also studies in mice suggest a role of retinoids in the contribution of delta oscillations to the sleep electroencephalography. Objectives The aim of this study was to investigate the effect of isotretinoin treatment on sleep architecture using polysomnography (PSG). Patients and methods Twelve severe acne vulgaris patients without any psychiatric and sleep disorders were treated with 0.5 mg/kg of isotretinoin. Clinician-administered acne questionnaire, psychiatric examination, Epworth sleepiness scale and PSG recordings were performed after the first month of treatment. Results Sleep efficiency was increased from 83.5% (62.889.0%, quartiles) to 89.5% (81.593.5%, quartiles; P = 0.036) and sleep latency decreased from 18.0 min (11.136.3, quartiles) to 15.5 min (9.319.0, quartiles; P = 0.023) following 1-month isotretinoin treatment. There were no significant changes in other sleep parameters of PSG and scores of Epworth sleepiness scale. Conclusions This study suggests that isotretinoin treatment slightly improves night-time sleep without any effects on sleep stages and daytime sleepiness.