An acid-pasting approach is developed in this work to prepare the composites of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) and carbon black (CB) by mixing both components in concentrated sulfuric acid. Different from the traditional powder processing, the solution-based fabrication strategy easily renders the effective combination of PTCDA and CB in the resultant CB/PTCDA composites, thus greatly improving their electrochemical performances. As the results, the composite with 20 wt% PTCDA shows excellent rate performances as the cathode material for both lithium ion battery (88 mAh g−1 at 5000 mA g−1) and sodium ion battery (100 mAh g−1 at 1000 mA g−1). As a facile and efficient processing strategy, the acid-pasting approach is expected to have wide application in the fabrication of organic electrodes in secondary batteries.