Al-mordenite and Fe-mordenite were synthesized with the tetraethylammonium as atemplate by hydrothermal method at 150 degreesC in the Na2O-Al2O3-SiO2-H2O and Na2O-Fe2O3-SiO2-H2O system, respectively. Synthesis of several Al-mordenites substituted with Fe, Al/Fe ratio = 75/25, 50/50, 25/75, were also attempted in the Na2O-Al2O3-Fe2O3-SiO2-H2O system under the same conditions by the hydrothermal method. The continuous solid solution of Fe in Al-mordenite was successfully obtained in mordenites with various Al-Fe molar ratios. Al-mordenite crystal was tablet-like with approximately 20-30 mum in diameter and 5-10 mum in thickness. Fiber-like Fe-mordenite grew up to 20-30 mum in length and 5 mum in diameter. The morphology of Fe-substituted Al-mordenite was cubic-like with 5-10 mum in size. The size of Fe-substituted Al-mordenite decreased with the increase of Fe-content.