<p>This study examines the influence of various surface treatments on the microstructure, residual stress, and tensile properties of high-strength Cr-Si spring steel subjected to induction hardening and tempering. Five surface conditions were evaluated: hardened and tempered (H&amp;T), shot peened (SP), nitrided (N), pre-shot peened followed by nitriding (Pre SP + N), and Pre SP + N with final shot peening (Pre SP + N + SP). Microstructural and surface modifications were characterized using scanning electron microscopy and X-ray diffraction. Pre-shot peening enhanced nitrogen diffusion during nitriding, leading to deeper nitride layers and increased compressive residual stress. While nitriding and its combinations improved surface hardness significantly, they also led to earlier fracture under tensile loading and slight reductions in strength and ductility. Fractographic analysis revealed surface-initiated cracks propagating via intergranular and quasi-cleavage modes. In the H&amp;T condition, dislocation hardening was the dominant strengthening mechanism, with secondary contributions from solid solution, grain boundary, and precipitation strengthening. Although nitriding improved surface hardness through nitride precipitation, it also reduced tensile strength due to dislocation recovery during thermal exposure. Among the treatments, Pre SP + N + SP offered the best balance, enhancing surface compressive stress while limiting the deterioration of core mechanical properties, making it a promising route for performance-critical spring steel applications.</p>