Soybean replacement of fish meaI is known to induce adverse effect in the liver and the mucosal lining of the intestine. The aim of the present work was to investigate the possible amelioration of the.deleterious· effects by addition of potassium dihydrogen phosphate and L. carnitine. For this purpose eighty sex reversed male fish were used, they were allocated into four groups, G1 control fed· on  a reference fish meal diet, G2 (S30)in which soybean replace 30% of fish meal, G3 soybean replace 30% of fish meal in addition to potassium dihydrogen phosphate KH2P04 (8.42%)and G2 & G3 with addition of L. carnitine ( l50mg/kg diet). The diet was prepared and provided to fish for 45 day, the initial and final body weight wee recorded. At the end of the experiment blood samples were collected for determination of serum glucose, total protein; albumen, cholesterol, triglycerides,· calcium, · phospherous, estradiol- l 7 (E2) and testosterone. Livers were weighed for calculation of HSI and histological sections from intestine and liver were prepared. The results revealed that body weight was significantly decreased in G2 and G3• HSI was significantly decreased in G3 and G4. There was a marked increase in serum glucose level in G4 as compared to other groups while serum total protein, cholesterol, triglycerides, Ca and P were significantly decreased in all groups as compared to control. However G4 showed a marked increase in serum testosterone level as compared to other groups. Histological findings showed shortening in mucosal folds and reduction in absorptive vacuoles in middle intestine beside vacuolation in hepatocytes in fish fed soybean diet. These tissues nearly returned to its normal structure in 04, which red L. carnitine added to the diet. It was concluded that partial replacement of fish meal by soybean had an adverse effect on body weight, some serum metabolites, sex steroids and normal morphology of liver and intestine. The results recommend addition of L carnitine to fish diets to improve body weight and reduce the adverse effect of hepatocytes and intestinal mucosa.