The catalytic properties of the passivated, reduced passivated, and fresh bulk molybdenum nitride for hydrazine decomposition were evaluated in a microreactor. The reaction route of hydrazine decomposition over molybdenum nitride catalysts seems to be the same as that of Ir/γ-Al2O3 catalysts. Below 673 K, the hydrazine decomposes into N2 and NH3. Above 673 K, the hydrazine decomposes into N2 and NH3 first, and then the produced NH3 further dissociates into N2 and H2. From the in situ FT-IR spectroscopy, hydrazine is adsorbed and decomposes mainly on the Mo site of the Mo2N/γ-Al2O3 catalyst.