N-Alloyed activated carbon fibers (ACFs) were prepared by chemical vapor deposition (CVD) of pyridine on pitch-based ACF at 973-1273 K for 30-120 min. The N-alloyed ACFs were characterized by Nz adsorption at 77 K, elemental analysis, scanning electron microscopy, and X-ray photoelectron spectroscopy (XPS). The nitrogen content increases due to the pyridine CVD. XPS examination showed that the percent of quaternary nitrogens of total nitrogen atoms deposited increases remarkably up to 91% by the CVD at 1273 K, even though the surface concentration of nitrogen atoms was only 2.0%. The morphological development and surface chemistry of N-alloyed ACFs treated by pyridine CVD depended on the CVD temperatures. The CVD treatment decreased the surface area and pore volume, while the average micropore width was not significantly changed. The pyridine deposition at 1273 K for 60 min was the best preparation method of nitrogen-deposited ACF (ACF/Py1213-60) with high microporosity and positively charged surface nitrogen atoms. The micropore width of ACF/Py1273-60 was smaller than that of ACF by 0.1 nm.