The synthesis of a continuous IMF zeolite membrane was fabricated on tubular substrates by seeded growth for the first time. The straight channels of IMF zeolite with diameters of 0.53–0.59 nm are distinguishable for p-xylene from o-xylene molecules. Pure IMF-phase high-silica IM-5 zeolite seeds with uniform and fine crystal size were fabricated by a new sonication-assisted aging process. The seeds were coated on the support by dipcoating and induced the formation of continuous membrane. Separation performance in p-/o-xylene mixture was investigated at various temperature and pressure. The typical IM-5 zeolite membrane had p-/o-xylene separation factor of 3.7. Our results suggest that IM-5 zeolite is a potentially good membrane material for the separation of xylene mixtures.