Synthesis of nitrogen-doped carbon fibers (CF) has been proved to be one of the most promising oxygen reduction reaction (ORR) catalysts which can replace the state-of-art Pt catalyst for non-noble metal-free light-weight devices. Polymers of Intrinsic Microporosity (PIM-1) is soluble in common organic solvents and can be tailored by functionalization owing to nitrile groups in the backbone. PIM-1 was functionalized to amide (hydrolyzed PIM-1), amine and amidoxime groups. The modified PIM-1s were electrospun into ultrafine fibers and pyrolyzed to obtain CF. The present article investigates the influence of different functional groups on the properties of PIM-1 based CF and their nitrogen-doping. Particularly, their ORR performance has been evaluated. Interestingly, CF from hydrolyzed PIM-1 have the highest pore volume with small pore size among the CF based on PIM-1, amine and amidoxime PIM-1. The amount of nitrogen-doping in these CF shows the trend according to the functional groups as PIM-1 > amine > amidoxime > amide. Among all these PIM-1 based CF; CF from hydrolyzed PIM-1 has the highest percentage of pyridinic and graphitic nitrogen, furthermore, electrocatalysis revealed that ORR processed through four-electron with the onset potential 985 mV vs. reversible hydrogen electrode (RHE) which is comparable with the standard Pt/C catalysts.