Abstract Barrows (n = 350; DNA 200×400; [n = 2,172; initial body weight (BW) = 6.0 ± 0.06 kg] were used in a 38-d growth trial to determine the effects of increasing folic acid on nursery pig growth performance and serum homocysteine. Pigs were weaned at 21 d of age and randomly allotted to 1 of 5 dietary treatments in a completely randomized design. A total of 70 pens were used with 5 pigs per pen and 14 replications per treatment. Dietary treatments were corn-soybean meal-based and consisted of increasing added folic acid: 0, 5, 10, 20, or 40 mg/kg. Treatment diets were fed in three phases from d 0 to 10 (phase 1), d 10 to 23 (phase 2), and d 23 to 38 (phase 3) after weaning. For phase 1, there were no differences (P > 0.10) in BW, average daily gain (ADG) and average daily feed intake (ADFI) across treatments (Table). However, increasing folic acid resulted in decreased gain to feed ratio (G:F; linear, P = 0.032). For phase 2, there was a marginally significant response in BW, ADG, and ADFI where performance was decreased as folic acid increased with the poorest performance observed when pigs were fed 20 mg/kg (quadratic, P ≤ 0.079). No treatment differences (P > 0.10) were observed for G:F. For phase 3 and overall (d 0 to 38), final BW, ADG, ADFI, and G:F were reduced with increasing folic acid with the poorest performance observed when pigs were fed 20 mg/kg (quadratic, P ≤ 0.049). No differences (P > 0.10) were observed for mortality or removals across treatments with a very low amount of overall mortality. On d 10 and 23, blood samples were collected from 70 pigs to determine serum homocysteine concentrations. A marginally significant treatment × d interaction was observed (linear folic acid × d, P = 0.069). An increase (linear, P = 0.037) in homocysteine concentrations was observed as folic acid increased from 0 to 40 mg/kg in the diet on d 10; however, no differences were observed across increasing folic acid treatments on d 23 (P = 0.450). Pigs had increased (P < 0.001) homocysteine concentrations on d 10 compared with d 23. In summary, the addition of folic acid resulted in reduced growth performance with the greatest impact observed when pigs were fed 20 mg/kg.