Aflatoxins, especially aflatoxin B1 (AFB1), can be greater in dried distillers grains with solubles (DDGS) because it can be concentrated during the ethanol production process. Increased use of DDGS in swine diets could potentially lead to an increased incidence of aflatoxicosis, a disease associated with decreased feed intake, reduced BW gain, and impaired liver function. The objective of this study was to determine the effects of AFB1 on the health, performance, and serum profile of growing barrows. Ninety Duroc × Yorkshire crossbred barrows were purchased (age = 35 ± 5 d; BW = 14.2 ± 3.0 kg), allocated to 9 pens with 10 pigs per pen, and randomly assigned to receive diets containing 0 µg/kg of AFB1 (CON), 250 µg/kg of AFB1 (LO), or 500 µg/kg of AFB1 (HI) for 7, 28, or 70 d in a 3 × 3 factorial arrangement of treatments. Feed intake was measured daily, and pigs were weighed and blood samples collected weekly. Serum was analyzed for concentrations of aspartate aminotransferase (AST), alanine aminotransferase (ALT), total bilirubin (BILI), and blood urea nitrogen (BUN). Both ADFI and ADG were negatively affected (P ≤ 0.001) by AFB1 treatment. Average daily feed intake was less (P < 0.05) in HI barrows than in CON barrows from wk 5 to 10 and was less (P < 0.05) in LO barrows than in CON barrows in wk 5 and again from wk 8 to 10. Also, ADFI was less (P = 0.022) in HI barrows than LO barrows in wk 10. Decreased ADG (P < 0.05) was observed in HI barrows than in CON barrows in wk 8 and 10; no differences (P ≥ 0.665) in ADG were noted between CON and LO barrows. There was no effect (P ≥ 0.080) of AFB1 treatment on ALT or BILI concentrations. However, both AST and BUN were affected (P < 0.05) by AFB1 treatment. Serum AST was greater (P = 0.010) in LO barrows than CON barrows in wk 5, and serum BUN was greater (P = 0.004) in CON barrows than LO barrows in wk 3. Results from this study demonstrate that the performance and health of young growing barrows were affected by consumption of an AFB1-contaminated diet, especially when fed for a more extended period.