Camel milk plays an important source of nutrients in arid lands and consumed as fresh ,pasteurized and fermented. This study aimed to evaluate the effects of camel and cow casein hydrolysates by trypsin enzyme on rheological and sensory properties and growth of starter culture of yoghurts made from cow milk. Caseins were separated from camel and cow milk ,and hydrolyzed by trypsin enzyme. The hydrolysates were added at concentration of (0.5; 1.0 and 1.5%) to yoghurt made from cow milk. Results showed that casein hydrolysates strongly decreased the fermentation and coagulation time of the yoghurts. The rate of pH decrease was higher with camel casein hydrolysate in comparison with cow casein hydrolysate at all concentrations (0.5; 1.0 and 1.5%) Viscosities of the yoghurt made with hydrolysates significantly (p蠄0.05) decreased than control samples. The addition of the hydrolysates significantly (p蠄0.05) increased the hardness and adhesiveness of the yoghurts. No significant differences in water holding capacity of control and treated samples were observed . However, increasing casein hydrolysate addition to 1.5% decreased water holding capacity of yoghurt samples. The sensory evaluation scores of the yoghurts were significantly (p蠄0.05) improved with the addition of casein hydrolysates.