Processing efficiency of rainbow trout, amounts of by-products and their nutritional value as well as some correlations between whole fish weight and products yield were evaluated. Results showed that efficiency decreased up to 87.56 ± 3.43% for gutted fish and it reached up to 56.69 ± 3.26% and 45.36 ± 2.37% for skined on and skinless fillets, respectively. The highest amounts of by-product were related to head and viscera which were 15.52 ± 2.00% and 12.62 ± 2.61% of body weight, respectively. A significant negative correlation was found between fish weight and head weight percentage (P<0.01). Also, the yield of headed and gutted product increased significantly by increase in fish weight (P<0.01). Among by-products, viscera and head were the richest sources of fat (17.4 and 13.0 % of wet weight) and skin contained the highest amount of protein (24.1% of wet weight). Moreover, a significant presence of the most important and health benficial omega-3 fatty acids was detected in both head and viscera. Viscera and bone were also found as rich source of iron mineral.