Background: In the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) the night eating syndrome has been classified as one of other specified feeding or eating disorders. It is estimated that this syndrome affects about 1.5% of the population; the prevalence of its familial form is not known. Material and methods: The study applied the Pittsburgh Sleep Quality Index, the Mini-Addenbrooke’s Cognitive Examination, the Rey–Osterrieth Complex Figure Test, the Trail Making Test, the Auditory Verbal Learning Test, the Beck Depression Inventory, the State-Trait Anxiety Inventory and free diagnostic methods. Case description: The paper presents a case of a 35-year-old female patient hospitalised due to sleep disorders and episodes of night binge eating occurring for about 15 years. The performed examinations did not reveal any depressive, anxiety or positive symptoms nor symptoms indicating anorexia or bulimia. The neurological examination did not reveal any deviations from normality which was confirmed by the imaging examination of the head performed with a contrast agent, by the electroencephalographic examination and by biochemical examinations. The family history indicated the occurrence of similar symptoms in two family members. Results: The results of the psychological examination confirmed the lowering of sleep quality and the deterioration of cognitive functioning in the aspect of short-term verbal memory and of the ability to concentrate attention as well as the lowering of the level of semantic fluency in a narrow scope. Conclusions: Performing differential diagnostics resulted in diagnosing a familial form of the night eating syndrome. Considering the low prevalence of the discussed illness in the population, there is a necessity to deepen the research related to this form of the syndrome.