The effect of precursors on the active phase formation and hydrodesulfurization activities of noble metal phosphide catalysts was examined. The maximum activities of Pd-P and Rh-P catalysts prepared from acetylacetonato (acac) complex were observed at lower reduction temperatures than those for catalysts prepared from chlorides (Cl). The Pd-P catalyst prepared from acac also showed higher activity than that obtained from Cl. However, this trend was not observed in the Rh-P catalyst. The characterization results revealed that the higher activity of the Pd-P catalyst prepared from the acac is due to the highly dispersed Pd4.8P.