Lignin derived from lignocellulose biomass such as oil palm empty fruit bunches (OPEFB) was converted into vanillin through depolymerization reactions in the presence of NiO/HY zeolite. Beforehand, lignin was isolated from black liquor from delignification of oil palm empty bunches using sulfuric acid (19% acid insoluble lignin). Zeolite NaY as a catalyst was synthesized with a molar ratio of 4.3Na2O: 10SiO2: Al2O3: 180 H2O. The as-synthesized NaY is then was modified to HY and impregnated with 10% of nickel oxide (NiO/HY). The zeolites were characterized using FTIR, XRD, BET and SEM-EDX. The lignin depolymerization reaction was carried out using methanol-water mixture as a solvent and NiO/HY as catalyst. Lignin depolymerization reaction was carried out at various temperatures including 150°C, 200°C and 250°C to determine the optimal temperature of the highest yield of vanillin. The reaction results were analyzed using liquid chromatography (HPLC). The results showed that the depolymerization reaction took place optimally at 200°C in the presence of NiO/HY catalyst for 30 minutes.