Low temperature CO adsorption followed by IR spectroscopy (IR/CO) characterization was used to depict the MoS2 morphology change with sulfidation temperature on MoS2/Al2O3 catalyst. It is found that the morphology of MoS2 slabs on MoS2/Al2O3 catalyst under typical sulfidation temperature range (573 to 723 K) is a truncated triangle exposing both the M-edge and S-edge. Moreover, the IR/CO data indicate that the truncation degree (ratio of S-edge/M-edge) of MoS2 slabs gradually increases with increasing sulfidation temperature. This finding is in line with density functional theory calculation on model catalysts, providing IR evidence of MoS2 morphology change with sulfidation temperature on an Al2O3-supported catalyst. As a further step, it is also found that the MoS2 morphology is strongly influenced by MoS2–Al2O3 interactions under the same sulfidation temperature.