This study investigated whether the immunocompetence of piglets at weaning was modulated by including different sources of n-3 polyunsaturated fatty acids (PUFA) in the maternal diet. From day 73 of gestation until weaning at 4 weeks, 32 pregnant sows were fed a palm oil-based diet (control group) or a diet including 1% linseed oil (C18:3n-3), 1% echium oil (C18:3n-3, C18:4n-3, C18:3n-6) or 1% fish oil (C20:5n-3, C22:6n-3). It was hypothesized that each diet would differently affect immune function through effects such as specific eicosanoid production. Piglets were fed a conventional diet without added n-3 PUFA from weaning until day 35 post-weaning. At weaning and 21 days post-weaning, four piglets per litter were immunized with bovine thyroglobulin. Blood samples were taken from weaning until day 35 post-weaning to determine thyroglobulin-specific antibodies, serum amyloid A (SAA) concentration and fatty acid composition. The fatty acid composition of the maternal diets was reflected in the plasma and red blood cells of the weaned piglets. The onset of the thyroglobulin-specific IgM response differed between dietary groups, with a delay in response for piglets from sows fed the fish oil diet. No significant dietary effects were observed on the thyroglobulin-specific IgG and IgA titres or on SAA concentrations in the piglet serum. Including n-3 PUFA in the maternal diet at the concentrations used in the present study had no major effects on the adaptive and innate immunity of the piglets after weaning.