Flexible piezoelectric nanogenerators (PNGs) that convert mechanical vibrations into electrical energy, have attracted great interest in light of the ever-growing demand for wireless, portable, implantable, and/or wearable self-powered devices, and the ubiquitous availability of ambient vibrational energy sources as a potential power solution. Compared to their ceramic counterparts such as barium titanate and lead zirconium titanate, piezoelectric polymers possess a range of advantages including lightweight, flexible, and ease of processing, in spite of relatively weaker piezoelectric properties. Odd-numbered Nylon-11 (PA11) has been known to possess ferroelectric and piezoelectric characteristics by virtue of the high degree of hydrogen bonding and dipole orientation resulting from the arrangement of polyamide molecules within adjacent chains among crystallization. PA11 exhibits five different polymorphs, i.e., alpha, beta, gamma, delta, and delta’, wherein the delta’ form shows the highest piezoelectric performance. In this work, we propose a facile and scalable strategy based on electrospinning technique to prepare PA11 nanofiber membranes mainly composed of the delta’form. The piezoelectric performance of PA11 nanofiber membranes as energy harvesters was comprehensively studied in terms of the open-circuit voltage, short-circuit current, and output power. Further, the understanding of the piezoelectric properties in relation to the crystal structure and orientation in nanofibers was elaborated in depth.