Polyaniline-modified carbon nanofibers were prepared in the presence of five different dopant acids, namely toluene sulfonic acid (TSA), hydrochloric acid (HCl), sulfuric acid (H2SO4), phosphoric acid (H3PO4) and camphor sulfonic acid (CSA), by oxidative polymerization. A comparative study on the effect of various types of dopants on the properties of PANI/CNF composite was performed. The electrical, dielectric and thermal properties of PANI/CNF composites were studied in contrast to pure PANI. Unlike polyaniline, all polyaniline/carbon nanofiber combination resulted in enhanced electrical and dielectric properties. Higher conductivity and thermal dependence of DC conductivity were obtained for toluene sulfonic acid-doped composite. UV-Vis analysis of the composites showed that the appreciable increase in conductivity of TSA-doped PANI/CNF composite is due to the extensive electron transfer. Further, thermogravimetric analysis showed improved thermal stability compared to PANI. A significant improvement is observed for organic acid-doped composites which suggest the presence of strong interaction between pi orbitals of CNF and the quinoid rings of PANI. Hence, the study indicated that the dopants had a remarkable effect on the properties of PANI/CNF composites.