The catalytic pyrolysis of waste Korean pine nut shell (KPNS) over mesoporous Al2O3 was investigated by thermogravimetric analysis (TGA) and pyrolyzer-gas chromatography/mass spectrometry (Py-GC/MS). TGA results showed that the thermal and catalytic pyrolysis of KPNS over mesoporous Al2O3 has the same decomposition temperature. On the other hand, the maximum decomposition for the catalytic pyrolysis of KPNS over commercial-Al2O3 shifted to a higher temperature. The Py-GC/MS results indicated that large amounts of oxygen-containing pyrolyzates, such as acids, furans, levoglucosan, and phenols, were produced by the non-catalytic pyrolysis of KPNS. These oxygen-containing pyrolyzates were upgraded efficiently into aromatic hydrocarbons by applying Al2O3 catalysts. Between the two Al2O3 catalysts, mesoporous Al2O3 showed better performance on the formation of aromatic hydrocarbons via the catalytic pyrolysis of KPNS than commercial Al2O3 because of its uniform larger pores.