This study investigates the mechanical properties and unique structural features of nanofiber yarns produced via electrospinning. Through experimental, analytical, and numerical methods, the tensile behavior of the yarns was evaluated. Nanofiber yarns, composed of submicron-diameter fibers, exhibit a significantly larger surface area and stronger fiber interactions compared to conventional yarns. These structural characteristics result in a marked improvement in mechanical properties, with the nanofiber yarns showing a 25% increase in stiffness and a 15% enhancement in damping capacity. A three-element viscoelastic model was applied to accurately describe the nonlinear tensile response of the yarns, with a high correlation to experimental data (R2 > 0.999). Furthermore, nanofiber yarns demonstrated superior thermo-mechanical stability, with a tan δ peak observed at 108 °C, compared to 100 °C for conventional yarns. These findings suggest that nanofiber yarns are promising candidates for applications in tissue engineering, filtration, energy storage, and other high-performance fields. The research provides a solid foundation for further optimization of nanofiber yarns to fully exploit their mechanical potential.