Electrospinning using positive and negative polarity applied voltages is used to produce polyamide nanofibers with tailored surface functionality. The surface free energy of the resultant nanofibers is characterized from individual nanofiber wetting experiments. The polar contribution to the total nanofiber surface energy is seen to vary with the polarity of the applied voltage used. A mechanism to describe the change in the nanofiber surface free energy with electrospinning polarity is proposed, based on the formation of either positive or negative charges at the liquid jet-air interface during the electrospinning process. These charges at the liquid jet-air interface cause molecular orientation of chemical functional groups of the polymer chains during electrospinning and the mechanism is supported by subsequent grazing angle X-ray photoelectron spectroscopy (XPS) of the nanofiber surfaces. A one-step electrospinning process is therefore demonstrated to tailor specific chemical functionalities at polymer nanofiber surfaces.