The pediatric narcolepsy population is increasingly being recognized. The spectrum of this disorder is quite broad in its presentation, resulting in delayed diagnosis. A 3-year-old girl presented at our hospital with excessive daytime sleepiness, slow and inarticulate speech, and losing balance when standing or walking. Neurologic examination, laboratory test and brain magnetic resonance imaging (MRI) findings were normal. During follow-up, she had difficulty holding her head up or standing straight while laughing, and showed frequent nocturnal awakenings. Long-term video EEG monitoring revealed no abnormal slow or epileptiform discharge during head dropping or falling down. The polysomnography ( PSG) with multiple sleep latency tests (MSLT) demostrated poor night sleep and sleep onset REM sleep. Additionally she had HLA DQB1*0602. We report a case of early-onset narcolepsy presenting with excessive daytime sleepiness and cataplexy.