Hydrocracking of naphthalene as a model compound of polyaromatics to mono-aromatic hydrocarbons including benzene, toluene, ethylbenzene and xylene (BTEX) had been investigated over various modified zeolite supported catalysts under a mixed hydrogen (H-2) and methane (CH4) atmosphere. Among them, the 5 wt% Zn/HY (Si:Al ratio of 30) exhibited the best catalytic performance with a naphthalene conversion of 98% and a BTEX selectivity of 82%. Compared to those from the control experiment conducted under its H-2 and N-2 counterparts, the superior catalytic performance achieved under the environment of CH4/H-2 mixture leads us to infer that methane presence might exert a positive impact on directing the reaction pathway to produce BTEX during hydrocracking of naphthalene, resulting in notably enhanced liquid yield and BTEX selectivity accompanied with reduced coke formation. Pyridine and ammonia were used as probes to investigate the catalysts' surface acidity and it was found that Bronsted acid sites with moderate medium acidity play an important role in the selective hydrocracking of naphthalene into BTEX under H-2 and CH4 environment.