Ceramic honeycomb filter supported zeolite membrane modules were prepared by a novel microwave-assisted in-situ crystallization method. The synthesis was done in two stages; microwave heating of substrates saturated with precursor solution to form a thin layer of zeolite nuclei (seeds) on the porous substrates followed by hydrothermal treatment to crystallize the ZSM-5 zeolite on the substrates. Zeolite formation was significantly enhanced by comparison with the conventional hydrothermal method, as evident from XRD and BET surface area results. The degree of film formation was varied with varying the dipping time of the substrates in the precursor solution prior to microwave heating, thereby controlling film formation inside the pores of the substrates. This new method of seeding using a simple domestic microwave oven was employed to zeolite membrane modules by forming a zeolite film on the thin walls of a honeycomb filter. The permeability of single gases and the separation of mixed gases were evaluated, showing a low pressure-drop and high permeating flux of light molecule gases.