This paper highlights the effect of solvent vapor treatment on characterization of electrospun nanofiber membrane (ENM). Fouling issue in membrane separation has becoming a debate since it reduces the lifetime of the membrane. In order to solve this issue, ENM has been recommended due to its great performance in terms of filtration, permeability and stability. However, ENM has several drawbacks such as low mechanical strength and loosely packed layers of nanofibers. Thus, solvent vapor treatment was used to solve this issue. In this study, nylon 6, 6 was fabricated as ENM and was exposed to formic acid as solvent vapor treatment. Solvent vapor treatment helps to increase the bonding of fiber by promoting crosslinking at the junction of fiber thus making the membrane mechanically durable. By controlling the solvent vapor exposure time, excessive fusion between the fibers can be prevented as over-crosslinking would reduce membrane permeability. Solvent vapor treatment also reduces the number of layers of ENM, by making it more closely packed and reduces the risk of membrane delamination. All treated ENM were found to be more hydrophilic and has lower surface roughness, which would make them more resistant towards fouling than the untreated one. © Published under licence by IOP Publishing Ltd.