Soy proteins possess a well-balanced amino acid composition, and numerous studies indicate a positive effect on muscle mass formation and stimulation of muscle growth. The aim of this study was to examine the effect of soy protein hydrolysate on the proliferation, differentiation, and morphological changes of mouse C2C12 myoblasts. The cells were treated with soy hydrolysate in a concentration range of 0,5-5 mg mL⁻¹ , and cell viability was determined after 48 hours using the MTS method. The effect of 1 mg mL⁻¹ soy hydrolysate on the differentiation of C2C12 cells was monitored over seven days, and the effect of 1 mg mL⁻¹ hydrolysate on the atrophy of C2C12 cells induced by 100 μM dexamethasone was monitored over two days. The obtained results showed an inhibitory effect of the addition of soy hydrolysate on the viability of C2C12 cells at all tested concentrations. However, the addition of soy protein hydrolysate at a concentration of 1 mg mL⁻¹ increased the diameter of myotubes during the differentiation of C2C12 cells by 12 %. The addition of 1 mg mL⁻¹ soy protein hydrolysate in the presence of 100 μM dexamethasone increases the diameter of myotubes almost to control values, indicating its potential protective effect in myotube atrophy. Comparing the morphology of control and treated cells with 1 mg mL⁻¹ soy hydrolysate, no significant differences were observed in the appearance of the C2C12 cell monolayer.