BACKGROUND Late preterm infants have higher morbidity in the neonatal period and difficulties at school age. There are few data about neonatal neurobehavior performance that may interfere in their development. OBJECTIVE To compare the neurobehavior of healthy late preterm and full-term neonates born to adolescent mothers. METHODS This prospective cross-sectional study included infants with a gestational age of 40(0/7)-40(6/7) weeks (full term) and 34(0/7)-36(6/7) weeks (late preterm) aged 24-72 h without exposure to alcohol, tobacco, drugs or infections and free of clinical problems during the first 3 days of life. Infants were assessed with the Neonatal Intensive Care Unit Network Neurobehavioral Scale (NNNS). Outcomes were analyzed by ANOVA. RESULTS From July 2001 to November 2002, 3,685 infants were born, 928 of adolescent mothers. After exclusion, 36 late preterm and 96 term infants were enrolled. Adjusted for anesthesia type, delivery mode, gender, age at NNNS examination, time between last feeding and examination, and examination duration, late preterm, compared to term neonates, presented lower scores for attention (p = 0.041), arousal (p = 0.011), regulation (p < 0.001), quality of movements (p < 0.001) and higher scores for non-optimal reflexes (p < 0.001) and hypotonicity (p = 0.029). CONCLUSIONS Late preterm infants of adolescent mothers have a more immature neurobehavioral performance at 24-72 h of life in multiple areas compared to term neonates suggesting a need for careful follow-up.