Abstract: In the laser powder bed fusion (LPBF) manufacturing process, residual stresses caused by temperature gradients significantly affect the service life of parts. Thermal-vibration aging, as a novel stress-relief method, can efficiently and rapidly alleviate residual stresses and improve mechanical properties. However, the effectiveness of this method in controlling residual stresses and mechanical properties in LPBF-Ti-6Al-4V alloys remains unclear. Therefore, residual stress variations along the axial direction (AD) and tangential direction (TD), together with tensile properties, Vickers hardness, and fracture morphology of the specimens were systematically analyzed. The results indicate that thermal-vibration aging significantly reduces residual stress. After treatment at 550 °C, residual stress decreased by 76.91% in the AD direction and by 74.85% in the TD direction. In terms of mechanical properties, the combined effect of high-temperature vibration not only released residual stresses but also significantly improved plasticity; the elongation of the 550 °C thermal-vibration-treated samples increased to 11.0%, the tensile strength remained at 1 258.5 MPa, and the hardness reached approximately 371 HV_0.5. Fracture surface examination revealed that thermal-vibration treatment resulted in a mixed brittle-ductile fracture behavior, with an increase in the number of ductile dimples and their uniform distribution, further indicating improved plasticity. In summary, thermal-vibration aging treatment can effectively improve the residual stress state and strength-plasticity balance of LPBF-Ti-6Al-4V alloys, providing a reference for the fabrication of high-performance components.