This is the first report of a neonatal withdrawal syndrome associated with maternal hydroxyzine treatment (150 mg/day) confirmed by measurements of hydroxyzine plasma concentrations in the mother and infant after birth. Hydroxyzine plasma concentrations were measured by liquid chromatography-mass spectrometry. Neurological symptoms with low neonatal concentrations of hydroxyzine may be due to a withdrawal syndrome. According to previous observations and this case report, clinicians should be warned of this possible rare neurological complication of hydroxyzine in neonates born from long term treated mothers.