Environmental issue about Hazardous and Toxic waste in industrial is the most important thing to consider nowadays. The rapid development of industries makes catalyst to be the best answer to make the reaction of a process becomes more fast. Hydrotreating process is one of the example that use catalyst as its requirement. The process produces spent catalyst as its waste containing nickel within 72438.59 mg/kg which led us to the needs of recovery. Leaching is known as an effective way to recover metal from a spent catalyst. In this study, nickel is recovered from the spent catalyst by varying some operating parameters in the leaching process such as the concentration of citric acid and EDTA from 0.1-0.3 M, the temperature from 55-85°C, and the time from 30-480 minutes. The results obtained show that leaching of about 59.45% was achieved under the following conditions: average particle size 150 mesh, temperature 75°C, reaction time 240 minutes, stirring speed 750 rpm, citric acid concentration 0.3 M and solid/liquid ratio 1:50 g/ml. The activation energy value is 10.08 kJ/mol which indicates that diffusion through the product layer is the rate controlling process during the reaction.