The effects of tetralin as an H-donor on the reactivity of asphaltenes in a petroleum pitch were investigated under thermal cracking or catalytic hydrocracking conditions at 693 K and 10.0 MPa N-2 or H-2. Reaction temperatures, pressures, and tetralin contents were varied to examine the reactivity of asphaltenes. Thermal cracking of the petroleum pitch led to a considerable amount of coke formation, close to 53.7 wt%, but the addition of tetralin reduced the coke formation down to 23.6 wt%. The coke formation was considerably reduced to 10.3 wt% in the catalytic hydrocracking condition, and was not formed in the presence of tetralin. Kinetic studies on the catalytic hydrocracking of petroleum pitch in the absence or presence of tetralin demonstrated that the addition of tetralin, showing an increase in the hydrogen transfer capacity, contribute to the marked performance of hydrocracking of the petroleum pitch in the presence of dispersed MoS2 catalyst.