The present study was conducted to evaluate the effect of feeding of different levels of metabolizable energy and of different crude protein levels on the performance and blood factors in Japanese quails in their 5 to 41d old. The experiment was conducted as a 3×5 factorial arrangement, in a completely randomized design of four replicates with 40 quails per replicate. The fifteen dietary treatments consisted of three levels of dietary energy (2800, 2900 and 3000 kcal ME kg⁻¹) times five levels of crude protein (22, 23, 24, 25 and 26%). Blood samples were collected towards the end of the study to determine Thyroxine (T4), Triiodothyronine (T3) and cholesterol content. There was no interaction observed between the two factors (P>0.05). Daily weight gain of quails fed diets containing 3000 Kcal ME kg⁻¹ was significantly higher than thoseted at the other levels (P< 0.001). Also, final body weight increased with increasing ME level (P<0.05). Feed conversion ratio was lower in diets of 3000 kcal ME kg⁻¹ content in comparison with 2800 kcal ME kg⁻¹ (P< 0.05). ME level did not significantly influence feed intake (P> 0.05). T4 concentration for males fed 3000 kcal ME kg⁻¹ diet was significantly higher than T₄ in the other two treatments level (P<0.01). On in the other hand, T3 coentration in males declined using diets containing 2800 kcal ME kg⁻¹ (P<0.0001). Also T4 concentration in females and cholesterol concentration in both sex enhanced significantly with increasing ME level from 2800 to 3000 kcal ME kg⁻¹ (P<0.05). In spite of T4 concentration, none of the measured characters had been influenced by protein levels (P>0.05). T4 concentration of males was higher in diets 26% crude protein in comparison with diets containing 22% and 23% crude protein (P<0.05). Also, female quails fed with diets containing 25% and 26% crude protein had higher T4 concentration than those fed with other diets (P<0.01).