Hydrazine in water and soil has caused serious diseases that threaten human health. It is critical to develop a simple and effective method for hydrazine detection. In this work, a simple fluorescent probe (BP) for hydrazine detection was synthesized from the isoquinoline alkaloid berberine. The probe has a short synthesis route (2 steps), low detection limit (1.37 μM), excellent fluorescence properties, and convenient naked-eye detection. In addition, BP displayed excellent selectivity and specificity over other metal ions, anions, and amines. Moreover, BP was also successfully used to detect hydrazine gas at different concentrations.