The objective of this study was to evaluate effects of yeast cell wall (YCW) supplementation in weaned piglet’s diet on performance and diarrhea incidence. Trial 1 was conducted on a swine farm which recently recovered from hog cholera disease, and 120 piglets, 28-d old (avg. 8.37 kg) were distributed in an randomized complete block design (RCBD), with 2 treatments (0 and 2 kg/MT of YCW from Saccharomyces cerevisiae), being 8 reps for control group and 7 for YCW group, of 8 piglets in each. The 2nd trial was conducted on a swine farm where the low disease profile was relatively stable for the past 2 years, and 100 piglets, 28-d old (avg. 7.53 kg) were distributed in RCBD, with 2 treatments (same as 1st trial) each having 5 reps with 10 piglets in each. The periods were 20 and 21d, respectively, for 1st and 2nd trials, divided into booster (28–30d) and pre-starter diets (31–47d 1st trial, and 31–48d 2nd trial). The parameters measured in both trials were: body weight (BW, kg), body weight gain (BWG, kg), average daily feed intake (ADFI, kg), feed:gain (F:G) and mortality (M, %). Diarrhea incidence (DI) was observed in 1st trial, and given a corresponding score from zero to 3 in order of increasing severity. The data were analyzed using the GLM (SAS), and means were compared by Kruskall-Wallis test for non-parabolic data. The YCW supplementation in the diet of weaned piglets resulted in no differences (P > 0.05) in performance parameters analyzed for both trials. However, the groups supplemented with YCW, numerically had improved BWG (+6.3; +6.4%) and F:G (+7%; 13.2%), respectively, for both trials. There were no differences (P > 0.05) between treatments for DI score. For control group, 90.36% of the population has 0 score at the beginning, which suggests a normal type of feces, and at the final week of the experiment, it minimally increased to 93.05%. For YCW group, there was an increase in the number of animals having a 0 score, from 82.58% to 93.79%, at the last week of the experiment. Supplementation of YCW at 2 kg/MT to diets of weaned piglets had numerical, but no significant, positive benefits when considering BWG, F:G, and DI, compared with control treatment.