The present experiment was conducted to investigate the effect of Polyzyme supplementation in low crude protein diets on Molar ducks on growth performance, carcass traits, some blood serum parameters, some histomorphological measurements, economic efficiency and European efficiency index. Two hundred and forty, un-sexed one day old White Molar duck chicks were used and assigned to eight groups nearly similar in average body weight, (3 replicates of 10 birds each). Polyzyme was added at the levels (0, 1, 2 and 3g/ Kg diet) to the low crude protein content that was used as a negative control (18 and 16 % CP) and the diet with normal content of crude protein, which was used as the positive control (20 and 18% CP) treatment during the periods of starter (1-21 days) and finishing (22-70 days), respectively.Results indicated that, ducks fed negative control + 3g Polyzyme/ Kg diet having the significantly higher body weight compared to the control groups. Birds fed the negative control diet with different levels of polyzyme had significantly (P ≤ 0.05) consumed more feed than the negative control diet without supplementation at 10 weeks of age.  Feed conversion ratio (FCR) and performance index (PI) were improved in birds fed negative control diet with 3g Polyzyme/ Kg diet, (T₄). Addition of graded levels of Polyzyme to Molar diets was significantly affecting some carcass traits and increased both serum glucose and AST activity, cholesterol, triglycerides and total lipids compared to the negative control group but significantly reduced serum createnine. Morphological sections of Molar small intestine revealed that villi height, width and villi height : villi width are significantly increased with the Polyzyme supplementation levels up to the level of 3 g/ kg diet and tend to decrease after that, but still better than the  negative control group. In general, and through the results obtained from feeding White Molar duck chicks from one day to 10 weeks of age on low crude protien diets (18 and 16%) with addition of different levels of commercial Polyzyme mixture (1, 2 and 3g/ Kg diet) improved growth performance due to increased activity of the small intestine and rate of nutrient absorption. The european efficiency ratio and performance index were improved when adding 3g Polyzyme/ Kg diet (4^th treatment ), while the economic efficiency and relative economic efficiency  were better (1.56 and 110.64, respectively) in the 2^nd treatment which chicks fed low crude protein diet +1g Polyzyme compared to the other trearments.