Composite catalysts containing molybdenum are mostly used for the purpose of hydrogenation in the oil refining industries. These treatment processes leave behind a large amount of used catalyst. These worn-out catalysts can be a secondary source of metal recovery for molybdenum and increase environmental awareness. In this paper, molybdenum recovery from worn-out catalysts has been investigated by leaching method in alkali medium (ammonia, NH3) after roasting process. The experimental data indicate that the roasting temperature and period, leaching temperature and duration are highly effective on the dissolution yield of molybdenum. The maximum dissolution rates of molybdenum (92.12%) was reached under optimum leaching conditions; roasting temperature, 600 degrees C; roasting time, 120 min; particle size, +75-30 mu m; liquid/solid ratio, 6 mL/g; ammonia concentration, 1 M; leaching temperature, 80 degrees C; leaching time, 90 min and stirring speed, 400 r/min. Kinetic results indicate that the dissolution reactions of molybdenum is controlled by the liquid film diffusion mechanism. Activation energy value (E-a) of molybdenum was found to be as 10.89 kJ/mol.