OBJECTIVE To compare the classification of the adequacy of birth weight for gestational age applying INTERGROWTH-21 (IG-21) and Fenton growth curves in preterm infants, and to relate this classification to the nutritional status at 12 months corrected age. METHODS This is a retrospective study with 173 preterm infants aged between 26 and 33 weeks. Data was collected on maternal health conditions, birth and gestational age anthropometric information, and anthropometry (weight, height, and head circumference) at 12 months corrected age. RESULTS The mean birth weight and gestational age were 1151.4 ± 227.2 g and 30.2 ± 2.4 weeks, respectively. Using percentiles of IG-21 and Fenton curves, the proportion of SGA and LGA preterm infants was 39.2% vs. 35.2%, and 3.5% vs. 3.5%, respectively (p = 0.520). At 12 months corrected age, short stature, overweight, and thinness were observed in 33.5%, 9.9%, and 11% of preterm infants, respectively. The ROC curve evidenced that the IG-21 was slightly better than Fenton to predict short stature (AUC = 0.626, 95% CI 0.537-0.715 and AUC = 0.600, 95% CI 0.506-0.694) and overweight (AUC = 0.648, 95% CI 0.527-0.769 and AUC = 0.618, 95% CI 0.486-0.750) at 12 months corrected age. In contrast, the ROC curve did not show an association of IG-21 and Fenton percentiles with thinness. CONCLUSIONS This study showed that IG-21 and Fenton were similar for the classification of birth weight for gestational age in preterm infants. IG-21 was slightly better than Fenton to predict overweight and short stature in preterm infants at 12 months corrected age.