The treatment of sleep disorders in Alzheimer’s disease (AD) may be quite challenging in elderly patients because of drug side effects or interactions and comorbid local or systemic diseases. Here, we report a patient with AD, who was suffering from severe insomnia and depression. We ordered agomelatine for the treatment of insomnia in this patient, and it was quite helpful not only for insomnia but also for depression and for the cognitive symptoms related with dementia. Our aim was to share these observations for similar patients.