Nanocrystalline ZSM-5 was prepared by using propyltriethoxysilane as an additive in the conventional ZSM-5 synthesis composition. Materials were characterized by a complementary combination of X-ray diffraction, nitrogen sorption, and Scanning electron microscopy. Transition metal ion exchanged nanocrystalline ZSM-5 (M-Nano-ZSM-5, where M = Cu2+, Ni2+, Co2+, Fe2+, and Mn2+) modified electrodes were constructed for the simultaneous determination of ascorbic acid (AA), dopamine (DA), uric acid (UA), and tryptophan (Trp). Electrochemical studies were carried out by using cyclic voltammetry, linear sweep voltammetry, and chronoamperometry in buffer solution at pH 3.5. Fe-Nano-ZSM-5 modified electrode exhibited excellent electrocatalytic activity with well-separated oxidation peaks towards AA, DA, UA, and Trp in their simultaneous determination. Among the M-Nano-ZSM-5 and transition metal ion-exchanged ZSM-5 (M-ZSM-5) materials investigated in this study, Fe-Nano-ZSM-5 exhibited the highest catalytic activities towards the oxidation of AA, DA, UA, and Trp with good stability, sensitivity, and selectivity. The analytical performance of this sensor was demonstrated for the simultaneous determination of AA, DA, UA, and Trp in blood serum and UA concentration in urine samples.