We report the case of a 22-year-old female victim of childhood sexual abuse with dissociative identity disorder and hypersomnia who remitted fromboth clinical conditions with the use of modafinil 400 mg/day. We review the literature supporting the sleep-dissociation theory, where trauma-relatedmemories induce a labile sleep-wake cycle allowing dreamlike mentation to intrude into waking consciousness and precipitate dissociative symptoms.The studies examined here found high correlations between dissociation and unusual sleep experiences. This may explain why in our case reportmodafinil, a medication with wake-promoting properties, improved both excessive daytime sleepiness and dissociation. Future studies are neededto determine which alterations in the sleep-wake cycle are most associated with dissociative disorders. We suggest a new perspective on the use ofmedications for comorbid hypersomnia, such as modafinil, in the treatment of dissociation.