The uniaxial tensile mechanical stress (MS) is induced up to 1.4 GPa on the junctionless channel of the twin junctionless nanowire (JL-NW) gate-all-around (GAA) field-effect transistors (FETs) using a four-point bending technique. The variation of the electrical parameters is measured before and during induced MS to analyze the performance. The ON-state current, carrier mobility, threshold voltage, and subthreshold swing are directly proportional to the induced MS due to the reduced energy band gap and intervalley scattering effect. The reduced subthreshold swing shows low power consumption and better switching ability in advanced CMOS technologies. In addition, the change of drain current shows highly piezoresistive sensing ability in nanoelectromechanical sensor applications. Thus, this study demonstrates the importance of mechanical stress engineering for performance improvement in CMOS technology, piezoresistive sensing applications, and device reliability.