Sixteen percent of adults ultimately diagnosed with having narcolepsy/cataplexy experienced symptoms before the age of ten years, 4.5% even before the age of five years. The symptomatology in childhood narcolepsy/cataplexy can differ significantly from adults and can lead to misinterpretations and misdiagnosis. Standard diagnostic tools (polysomnography and multiple sleep latency test) can give false negative results and do not exclude the disorder. The decision to determine hypocretins in cerebrospinal fluid (CSF) should be made as early as possible in children. Here, we present a case of a five-year-old girl with acute onset of narcolepsy/cataplexy after a closed head trauma. The first symptoms were excessive daytime sleepiness, partial facial cataplexy and a serious behavioral disorder. Hypocretin-1 level (Hrt-1) in CSF was undetectable.