Dementia is characterized by cognitive and also behavioral and psychological symptoms of dementia (BPSD). The most prominent BPSD are depression and apathy but sleep disorders also complicate the clinical course of dementia. These symptoms are a severe burden for patients and caregivers and are difficult to treat partly due to comorbidities. Common sleep disorders in dementia are insomnia, hypersomnia, circadian rhythm alterations and aberrant nocturnal motor behavior. Sleep duration and rapid eye movement (REM) sleep are reduced. The diagnostic assessment of sleep disorders should include an evaluation of the underlying risk factors and a detailed sleep history for which several assessment instruments are available. The therapy of sleep disorders of dementia is primarily nonpharmacological: sleep counseling, sleep hygiene regulation, relaxation and psychotherapy techniques are given priority. Pharmacological treatment often has severe side effects in this elderly, vulnerable population and can only be considered if other nonpharmacological options have been unsuccessful. The application of medication should be limited in time and dosage. The pharmacological therapeutic options are critically discussed in detail.