An experiment was carried out at the experimental farm of Tra Vinh University to evaluate the effects of replacing fish meal by fresh sea fish by-product (FSFB) on growth performance of ducks. Crossbred ducks (Cherry Valey x Pekin) at four weeks of age were arranged in a completely randomized design with 5 treatments and 3 replicates, with ten birds (balanced for sex) in each experimental unit. The treatments were levels of FSFB replacing fish meal protein at levels of 0, 25, 50, 75 and 100% corresponding to the FSFB0, FSFB25, FSFB50, FSFB75 and FSFB100 treatments. Replacing fish meal with sea fish byproduct led improvements in live weight gain and feed conversion up to the level of 75% replacement of the fish meal on a protein basis. It is suggested that the increased energy content of the sea fish byproduct, due to higher oil content may be compromised by the decreasing ratio of lysine (and other essential amino acids), relative to the increased energy status of the sea fish broduct as compared wiih fish meal. Carcass traits were not affected by the feedimg of sea fish byproduct. It is suggested that diets rich in sea fish byproduct may benefit from increased levels of supplementation with lysine and perhaps other essential amino acids.