Polymer nanospheres were synthesized through polymerization of resorcinol/formaldehyde (RF) in the presence of a basic amino acid, l-lysine, as a catalyst. The diameters of the RF polymer nanospheres can be tuned in the range of 30−650 nm by adjusting the molar ratios of l-lysine/H2O and resorcinol/H2O in the precursor solutions. The pH of l-lysine solution was reduced from 9.3 to 7.0 just after it was mixed with the RF solution, indicating that l-lysine molecules in the solution were consumed by interacting with resorcinol. As a result, particle growth rate extremely reduces. Thus, the particle size of the RF polymer was not much dependent with synthesis time. Thus, the use of l-lysine facilitates precise control of the size of the RF polymer nanospheres compared to the synthesis using an ammonia solution as a catalyst. Carbonized particles showed the same size as the RF polymer nanospheres. The resulting carbon nanospheres had mesopores and macropores with a surface area of 330−400 m2/g.