The objective of this study was to evaluate the effects of yeast extract complex derived from Kluyveromyces marxianus and Saccharomyces cerevisiae as a non-antibiotic functional product. In total, 150 crossbred weaning pigs [(Yorkshire × Landrace) × Duroc, 28-d-old] with an average body weight (BW) of 7.27 ± 1.47 kg were randomly allotted to one of three dietary treatments [five pigs per pen (two barrows and three gilts); 10 pens per treatment] for a 6 wk trial in three phases based on BW. Treatments consisted of corn–soybean-meal-based basal diet (CON) and basal diet supplemented with 0.2% or 0.4% yeast extract complex (YEC). The supplementation of 0.4% YEC to basal diet increased (P < 0.05) BW during phases 2 and 3 compared with CON. The average daily gain increased (P < 0.05) during week 1 and overall period, and gain to feed ratio was higher (P < 0.05) during phase 1 in pigs fed 0.4% YEC diets compared with those fed CON diets. In addition, the fecal Lactobacillus counts were increased (P < 0.05) with the supplementation of 0.2% and 0.4% YEC suggesting that 0.4% YEC supplementation could be used as non-antibiotic functional product.