This study evaluated the effects of feeding entrapped fish oil containing eicosapentaenoic (EPA; C20:5n-3) and docosahexaenoic (DHA; C22:6n-3) acids in chemically treated protein on fatty acid compositions and a-tocopherol concentrations of blood serum in lactating goats. The entrapped fish oil (EFO) were prepared with fish oil, defatted soy flour, and acetaldehyde. Nine Saanen lactating goats (4 yr old; BW = 48.3 ± 2.26 kg) were divided into groups of 3 and randomly assigned to 3 diets using a 3 × 3 Latin square design with 3 14-d periods. Experimental diets consisted of 95% basal diet, containing alfalfa meal, yellow corn and soybean meal, with 5.0% of oil/fat from either poultry fat (PF), fish oil (FO) or EFO. The designated diet was provided once daily ad libitum at individual feed stations. Blood samples were collected from individual goats at the end of each feeding period which were analyzed for α-tocopherol and fatty acid composition. All data were analyzed as a 3 × 3 Latin square design. Average daily intake of diet containing EFO was lower (P < 0.01) than diets containing either PF or FO (1.04 vs 2.56 or 1.90 ± 0.300 kg). Consequently, the ADG of goats fed EFO diet was lower (P < 0.05) than the other 2 diets. The blood serum from goats fed EFO diet tended (P = 0.08) to have a higher amount of α-tocopherol (2.31 vs 1.89 or 1.90 μg/mL) than did those from goats fed either PF or FO diet. Compared with goats fed PF-diet, goats fed either FO- or EFO- diet had higher (P < 0.01) concentrations of EPA (C20:5n-3, 1.76 vs 10.57 or 13.23%), docosapentaenoic (C22:5n-3, 1.32 vs 2.02 or 1.93%), and DHA (C22:6n-3, 1.95 vs 4.58 or 5.38%) acids in blood serums. Furthermore, the concentrations of EPA and DHA in blood serums from either EFO- or FO-diet fed goats were similar even with a limited intake of EFO-diet. Thus, feeding lactating goats with entrapped fish oil in chemically treated protein might protect n-3 fatty acids and α-tocopherols from ruminal degradation and subsequently increased those contents in the blood serum of lactating goats.