Zearalenone (ZEA), an estrogenic mycotoxin, is produced mainly by Fusarium fungi. Previous studies indicated that acute ZEA exposure induced oxidative stress and damage in multiple organs. Therefore, the present study was designed to investigate the adverse effects of dietary ZEA (1.1 to 3.2 mg/kg of diet) on oxidative stress and organ damage in postweaning gilts. A total of 20 gilts (Landrace × Yorkshire × Duroc) weaned at d 21 with an average BW of 10.36 ± 1.21 kg was used in the study. Gilts were housed in a temperature-controlled room, divided into 4 treatments, and fed a basal diet only (control) or basal diet supplemented with purified ZEA at a dietary concentration of 1 (ZEA1), 2 (ZEA2), or 3 (ZEA3) mg/kg of diet for 18 d ad libitum. The actual ZEA contents (analyzed) were 0, 1.1 ± 0.02, 2.0 ± 0.01, and 3.2 ± 0.02 mg/kg for control, ZEA1, ZEA2, and ZEA3, respectively. Gilts fed different amounts of dietary ZEA grew similarly with no difference (P > 0.05) in feed intake. Vulva size increased linearly over the 18 d of feeding in gilts fed diets containing 1.1 mg of ZEA/kg or greater (P < 0.001). Relative weight of genital organs, liver, and kidney increased linearly (P < 0.05) in a ZEA-dose-dependent manner. Serum aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, γ-glutamate transferase, urea, and creatinine (P < 0.05), and malondialdehyde concentrations in both serum and liver (P < 0.001) were also increased linearly in a ZEA-dose-dependent manner. However, spleen relative weight (P = 0.002) and activities of total superoxide dismutase and glutathione peroxidase (in both serum and liver (P < 0.05) were decreased linearly as dietary ZEA increased. Results showed that besides genital organs, the liver, kidney, and spleen may also be target tissues in young gilts fed diets containing 1.1 to 3.2 mg of ZEA/kg for 18 d. Increased key liver enzymes in the serum suggest progressive liver damage caused by feeding ZEA, and an increase in oxidative stress in gilts is another potential impact of ZEA toxicity in pigs.