Whey protein was added to hairtail surimi gel (HSG), the properties and structural changes were determined, and whey protein effects on them were investigated after incorporating 0.00% to 10.00% whey protein. Optimal results at 6.00% addition of whey protein were observed in texture, color, and water-holding capacity (WHC). Texture analysis exhibited a reduction in cohesiveness, resilience, and chewiness of HSG, while simultaneously increasing its firmness and springiness. Furthermore, the whiteness of HSG decreased by 5.00% and optimal WHC was observed at its maximum value. The electron microscopy images showed that HSG had a compact and smooth structure with a smaller pore size after whey protein was added. Nuclear magnetic resonance analysis demonstrated the gradual transformation of free water into immobile water in gel matrix, reaching up to 93.21%. Additionally, the formation of ionic bonds increased significantly to 2.954 mg/mL. Differential scanning calorimetry showed that the denaturation temperature of myosin was increased, however, that of actin was reduced. These insights contribute to surimi production optimization which can significantly enhance the functional characteristics of HSG, providing a basis for improved surimi-based products.