A total of 400 mixed parity sows (PIC Camborough, Hendersonville, TN) were used to evaluate the effects of increasing soybean oil supplementation prior to farrowing on sow and litter performance under commercial conditions. On d 111 of gestation, females were transferred to the farrowing room, blocked by parity and body weight, and allotted to one of four treatments within block in a randomized complete block design. Treatments included different amounts of soybean oil supplementation from d 111 to 113 of gestation, which included: 1) 0 g; 2) 250 g; 3) 500 g; 4) 1000 g. A corn-soybean meal-based diet containing 3.06% crude fat was fed and treatments were top-dressed at an equal amount for at least 3 d to achieve the designated supplementation level. The experimental data were analyzed using generalized linear mixed models with the GLIMMIX procedure of SAS. Polynomial contrasts were implemented to evaluate the linear and quadratic effects of increasing soybean oil supplementation. Response variables analyzed as normally distributed included sow body weight (BW) and caliper score at weaning, BW and caliper changes during lactation, piglet weight at birth, 24h after birth, and at weaning, colostrum yield, and litter average daily gain from cross-foster to weaning. Total born was analyzed following a poisson distribution and percentage born alive, stillbirth, and pre-weaning survivability were analyzed following a binomial distribution. Covariates were used if they significantly improved the model fit. Stillbirth rate increased (quadratic, P< 0.05) and percentage born alive marginally reduced (quadratic, P< 0.10) with increasing soybean oil supplementation up to 500 g, and then reduced and increased at 1000 g. There were no evidences (P >0.10) for linear or quadratic treatment effects for any of the other response variables evaluated.