Objective To evaluate the serum levels of adiponectin and leptin and their relationship with nutritional variables during pregnancy in adolescents. Methods This prospective cohort study evaluated eutrophic pregnant adolescents (body mass index [BMI], 18.5–24.9 kg/m 2 ) during the 3 gestational trimesters (first, 10–14 weeks; second, 24–28 weeks; and third, 30–34 weeks). Serum adiponectin and leptin concentrations were measured using the enzyme-linked immunosorbent assay method. The relationship of these adipokines with the pre-gestational BMI, gestational weight gain, weight at the time of sample collection, and newborn weight were evaluated. Analysis of variance and the Kruskal-Wallis test were used for statistical analysis. Results The study group comprised 62 pregnant adolescents. The serum concentration of adiponectin showed a significant difference between the first and third trimesters ( P =0.003), which decreased during pregnancy, but unrelated to nutritional variables. Serum leptin levels increased throughout the pregnancy ( P <0.0001) and showed a positive correlation with pre-gestational BMI, total weight gain, pregnancy weight at the time of sample collection, and newborns’ weight. Conclusion Serum levels of adiponectin and leptin vary inversely throughout pregnancy. This pattern in adolescents is similar to that observed in adults. Moreover, leptin concentrations increased throughout pregnancy, and they were positively correlated with all variables evaluated.