The present study investigated the effects of mannan oligosaccharide (MOS) supplementation of the diets of sows and/or their offspring on maternal and offspring performance and immune status. Sixty multiparous sows were fed either the control diet (sCON, n=30) or the control diet containing 400mg/kg MOS (sMOS, n=30) from d 86 of gestation until weaning. On d 7 of age, offspring were assigned within sow treatments to the piglet basal diet (pCON) or the piglet basal diet supplemented with 800mg/kg MOS (pMOS) for 28days. No dietary effect was observed on the number of total piglets born and born alive and the piglet weight at birth. Immunoglobulins concentrations in sow colostrum and milk were not affected by sow diet MOS supplementation (P>0.05). However, the weaning to estrus interval of sows was shortened significantly in the sMOS treatment compared with that of the sCON treatment (P=0.05). The weaning weight (P=0.03) and pre-weaning weight gains (P=0.01) of piglets from the sMOS sows were greater than that of piglets from the sCON sows. Furthermore, piglets from sMOS had higher serum concentrations of immunoglobulin A (IgA) (P<0.01), immunoglobulin G (IgG) (P<0.01), complement 3 (C3) (P<0.01), complement 4 (C4) (P=0.05) and lysozyme (LYZ) (P<0.01) at weaning, as well as C3 (P<0.01) and LYZ (P<0.01) on d 35 of age. Piglet dietary MOS improved both pre- and post-weaning weight gain (P<0.01) and increased serum concentrations of IgA (P=0.01) and IgG (P=0.01) at weaning, as well as C3 (P<0.01), LYZ (P<0.01) and C4 (P=0.01) on d 35 of age. Piglets coming from both supplemented groups, sow and piglet’s diets, showed the best performance and immune status at weaning and at 35 d of life. These results may suggest that those improvements at the pre-weaning stage may be partly derived by MOS sow’s supplementation, being additive its effect when MOS were also added in pre- and post-weaning piglet diets.