Hydrogen embrittlement (HE) remains a critical issue in industrial applications and academic research, particularly for low-alloy steels. To address this issue, this study developed a novel mechanical vibration-assisted thermoforming process, accompanied by self-developed equipment, to improve the mechanical properties and HE resistance of forged steels. The physical behaviours induced by the vibration field were leveraged to effectively generate hydrogen traps, thereby considerably improving mechanical performance and reducing HE sensitivity. Results revealed that the mechanical vibration-assisted process synergistically enhanced the strength and ductility of the forged samples while mitigating their HE susceptibility. In particular, the strength of the vibration-treated samples increased by 53.9% to 1330 MPa, while their ductility improved by 48.9%. Notably, the strength–elongation product increased by 131.0%, indicating a balanced enhancement in both properties. After H-precharging, HE sensitivity—characterised by the loss in elongation—decreased from 72.68 for the non-vibration samples to 63.14 for the vibration-treated samples, indicating a 15.1% reduction. Similarly, HE sensitivity based on area reduction declined from 71.15 to 60.57, demonstrating a 14.87% decrease. These findings highlight the effectiveness of the mechanical vibration-assisted process in improving both mechanical properties and HE resistance. To elucidate the underlying mechanisms, advanced characterisation techniques, including SEM, EBSD, FIB, and TEM, were employed. Based on the characterisation results, the improved strength of the vibration-treated samples was attributed to refined grain structures, uniformly distributed dislocations, finely dispersed precipitates and numerous slip bands within the grains. The primary strengthening mechanisms included grain boundary, dislocation and precipitation strengthening, with grain boundary and dislocation effects contributing prominently. Moreover, the stable structures formed by slip bands and grain boundaries further reinforced the overall strength. Fractographic analysis revealed conspicuous differences between the vibration-treated and non-vibration samples. The non-vibration samples exhibited brittle fracture features, including cleavage planes and intergranular cracks, while the vibration-treated samples displayed a mixed morphology of dimples and quasi-cleavage, indicative of enhanced toughness. TEM observations of the fracture zones in the vibration-treated samples revealed high-density dislocations and severe plastic deformation near the crack tips, suggesting the concurrent operation of hydrogen-enhanced decohesion (HEDE) and hydrogen-enhanced local plasticity (HELP) mechanisms during HE. In contrast, the non-vibration samples primarily exhibited HEDE, with hydrogen accumulation at precipitates and grain boundaries initiating and propagating secondary cracks, ultimately leading to brittle fracture. The reduced HE sensitivity of the vibration-treated samples was primarily attributed to the mitigation of conditions conducive to the HEDE and HELP mechanisms. Uniformly distributed dislocations, grains and precipitates promoted the dispersion of hydrogen and limited its accumulation at grain boundaries. Furthermore, interactions between hydrogen and slip bands broadened dislocation migration zones, enhancing resistance to hydrogen-induced cracking. In conclusion, this study presents a new approach for developing HE-resistant materials through mechanical vibration-assisted thermoforming. This process not only enhances the mechanical properties of forged steels but also considerably reduces their HE susceptibility, providing valuable guidance for industrial applications and future research in materials science and engineering.