Herein, we have prepared Polyaniline (PANI) nanofibers by interfacial polymerization in the presence of co-oxidant and surfactant. The additives are found to have a profound impact on the polymers morphology and improved room temperature conductivity. It was found that PANI nanofibers prepared in the presence of aqueous sodium hypochlorite solution (NaOCl) and cetyl trimethyl ammonium bromide (CTAB) were of shorter diameter (30 nm) and high conductivity (6.59Scm -1 ) than those formed in the absence of those chemicals. The diameter of the fibers was intricately tuned by changing the ratio of NaOCl to aniline. The effect of co-oxidant and surfactant concentration in the nanofibers has been investigated with the help of SEM, IR, XRD, UV and conductivity studies. A comparative investigation with other surfactant sodium dodecyl sulphate (SDS) has been done and the variations in diameter were noted. We also studied the third-order optical nonlinearity and optical limiting properties of polyaniline nanofibers using a single-beam z-scan technique. The experiments were performed with a Nd-YAG laser at wavelength of 532 nm The mechanism behind nonlinear absorption could be predicted as two photon absorption. The results show that the polyaniline nanofibers have useful applications in futuristic nonlinear optics.