This study sought to evaluate the anemia prevalence and effect of anemia treatment in pregnant adolescents.Methods: A cross-sectional study. Data from perinatal outcomes, serum hemoglobin level and iron supplementation were collected. Samples were divided into three groups: pregnant adolescents without anemia, with treated anemia and with untreated anemia. Frequencies, means, standard deviations and Chi-squared values were calculated. The significance level was 5%, and the software used was Epi-info 7.Results: The study included 458 pregnant adolescents. The mean age was 16 years old, and the prevalence of anemia was 41.27% (189). Mild, moderate or severe anemia were presented in 65.60%, 33.86% and 0.52%, respectively, of study participants. Among pregnant adolescents with anemia, 87.24% received treatment with iron supplementation. Preterm labor (p=0.003), gestational age at birth <37 weeks (p=0.036) and stillbirth (p=0.004) showed an association with nontreated anemia. Positive HIV was more prevalent in adolescents with nontreated anemia (p=0.018). The cesarean rate was 36.90%, with no difference between groups.Conclusion: Anemia is a public health problem among pregnant adolescents, and iron supplementation reduces negative neonatal outcomes. Treatment adherence by a multidisciplinary and qualified prenatal care team can be key in reducing adverse neonatal outcomes associated with pregnancy during adolescence.301011581162