A total of 96 weanling barrows were utilized in a 27 d experiment to determine the effects of post-weaning failure to thrive (PFTS) on organ weight, blood chemistry, and small intestine physiology and function. Thirty-two pigs from each of the lightest, median, and heaviest weight categories at weaning were placed in individual metabolism cages and allowed ad libitum access to water and a common nursery diet. After a 5 d acclimation period, growth rate was evaluated for 27 d. Pigs with ADG that were below two standard deviations from the mean were termed pigs with PFTS (n = 4). All other pigs were considered normal contemporaries. After the 27 d experiment, pigs were fasted overnight and humanely euthanized. Organs were emptied of digesta and weighed, blood was collected for analysis in a complete blood panel and white blood cell differential, and ileal samples taken for morphology and absorptive capacity analyses. Pigs with PFTS had increased (P < 0.02) stomach, intestine, kidney, and liver weights relative to body size. Additionally, PFTS pigs had decreased (P < 0.05) hemoglobin hematocrit, albumin, sodium, and anion gap concentrations, suggesting either anemia or increased dehydration compared to normal pigs. Finally, PFTS was associated with increased ileal villous crypt depth (P < 0.0001), but not with villous height or differences in absorptive capacity of various glucose or amino acids. These data suggest that pigs with PFTS may have a higher maintenance cost due to increased organ weight and a possible anemia or imbalance of blood chemistry. However, differences in post-weaning performance do not appear to affect small intestine function.