The aim of this article is to assess the psychological state of a narcolepsy patient whose emotional state and life quality deteriorated despite the accurate diagnosis and pharmacological treatment. Narcolepsy symptoms are: excessive daytime sleepiness, cataplexy, sleep paralysis, hypnagogic hallucinations, and disrupted nocturnal sleep. Despite the proper pharmacological treatment, the illness strongly influences social, professional and mental functioning. The first symptom, i.e. excessive daytime sleepiness, was observed by the patient during adolescence, but the first medical examinations took place at the age of 27, after the occurrence of the first cataplexy symptoms. After a few unsuccessful diagnoses, narcolepsy was diagnosed. The patient maintained her lifestyle, but due to feeling excessively tired and encumbered with duties at work, she decided to take a long-term sick leave. This change was self-assessed by the patient as beneficial for her psychophysical state: the stress level was lower and offered the possibility to adjust her daily schedule to the illness. The following methods were used: Beck Depression Scale, The Short Form (36) Health Survey and My Eating Habits Questionnaire. The results showed a medium severity of depression, lowered life satisfaction and tendency to emotional overeating. This may be a result of not fully developed stress and negative emotions coping strategies. The patient describes her social relations and professional functioning as not satisfactory due to the illness, which may result in depressed mood. Due to such results, there may be a need to expand treatment with psychoeducation, psychotherapy and antidepressant pharmacotherapy.