A series of novel Pt-Pd/polyfluorenes (PFs) composite catalysts were facilely prepared based on Pt/Pd precursor and PFs with hydroxyl and carboxyl substitution at the C-9 position by electrochemical method and their electrocatalytic performance toward formic acid oxidation were studied. Electrocatalytic experiments demonstrate that the Pt-Pd nanoparticles immobilized on poly(9-fluorenecarboxylic acid) (PFCA)-decorated glassy carbon (GC) electrode (Pt-Pd/PFCA/GC) show larger electrochemical active surface area, higher catalytic activity and stability toward formic acid oxidation than that of other Pt-Pd/PFs/GC, Pt-Pd/GC, as well as the commercial JM 20% Pt/C/GC electrodes, which can be attributed to the small-sized and well-dispersed Pt-Pd nanoparticles on PFCA matrix and the special electronic interaction between the metal nanoparticles and the polymer substrate. Moreover, the electron-withdrawing carboxyl substitution rather than the electron-donating hydroxyl on the polymer main chain is of great benefit to the removal of poison CO as well as the enhancement of catalytic activity of Pt-Pd toward formic acid oxidation. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.