Nanocrystalline ZSM-5 was prepared using propyltriethoxysilane. Materials were characterized by a complementary combination of X-ray diffraction, nitrogen sorption, and scanning electron microscopy. Transition-metal ion exchanged nanocrystalline ZSM-5-modified electrodes were constructed for the electrocatalytic oxidation of glucose and methanol. A non-enzymatic electrochemical sensor based on a Ni2+-exchanged nanocrystalline ZSM-5-modified electrode exhibits the highest sensing ability, whereas the corresponding Cu2+-exchanged electrode exhibits the highest current sensitivity for glucose oxidation. Among the variety of electrodes modified with transition-metal ion exchanged nanocrystalline ZSM-5, the Ni2+-exchanged electrode exhibits high current sensitivity and sensing ability in methanol oxidation. Electrocatalytic activity of conventional ZSM-5-modified electrodes was significantly low compared to nanocrystalline ZSM-5-modified electrodes. Enhancement in the electrocatalytic activities of nanocrystalline ZSM-5-modified electrodes can be correlated with the enhanced accessibility of glucose/methanol to M2+ active centers in the nanocrystalline ZSM-5 owing to its large specific surface area and intercrystalline mesopores. The sensor was applied directly to determine glucose concentration in adult human blood serum, and the precision of the method was found to be satisfactory. The non-enzymatic sensor exhibited excellent reproducibility, repeatability, stability, and antifouling ability for direct determination of glucose in human blood serum.