A series of novel palladium catalysts supported on carbon nanofibers of various nanostructures have been prepared, characterized, and tested in gas-phase synthesis of dimethyl oxalate. Significant improvements in both activity and selectivity have been achieved over well-defined carbon nanofiber supported palladium catalysts. Carbon nanofiber produced on 20% NiFe/Al2O3 (CNF-05) supported palladium catalyst possesses the highest activity, which can be ascribed to the high surface area of the support, relatively weak metal-support interaction, and smaller metal particles. The low metal-support interaction might improve the redox properties of the catalyst, and thus the activity. The functionalization of CNF-05 in air is found to dramatically increase the conversion of methyl nitrite compared to the functionalization in HNO3.