Alkali metal loaded zeolite X was used to catalyze O-alkylation of phenol derivatives in the presence of excess methanol. The reactivity of zeolite in the O-alkylation increased as the basicity of ion-exchanged metals increased. The super base originated from cesium oxide particles in zeolite cavities was as equally active as the ion-exchanged cesium cation. Hence the reactivity of the Cs loaded zeolite was found to be proportional to the total amount of cesium in zeolites. In addition to mono and dialkylphenols, the phenol derivatives with hydroxy, amino, nitro and chloride group were also used as reactants to investigate the effect of acidity of reactants on the reaction. The conversion increased as the acidity of hydroxy group of reactant increased. But the strong acidity resulted in rapid deactivation of the catalyst. Except for aminophenol the reaction products were the corresponding O-alkylated products regardless of functional groups attached and for aminophenol, N-alkylated product was produced due to the strong acidity of the amino group. The high selectivity to O-alkylation reaction over base catalyst was not a function of the conversion and thought to have resulted from the suppression of the side reactions such as C-alkylation of phenol and anisole which occurred predominantly on the acidic sites.