Modification of the carrier dynamics in correlated oxide systems via epitaxial strain is a promising pathway for the practical realization of energy-efficient electronic devices. Here we report on the thermally induced metal-to-insulator transition (MIT) of NbO2 films grown on Al2O3 substrates and the modulation of the MIT temperature via epitaxial strain from the substrate. The metal-insulator transition temperature (TMIT) increased from 910 to 1066 K with increasing strain. An ultrathin 3.9-nm film consisting of a single strained layer with minimal structural defects yielded a bulklike sharp transition. The substrate-induced strain offers another degree of freedom to improve device functionality of MIT materials.