Background/Objectives <p>This study aimed to investigate whether maternal body composition is related to blood and human milk metabolic hormones (adiponectin, ghrelin, and leptin) and whether these hormones are associated with infant body composition and anthropometric indicators.</p> Subjects/Methods <p>Fifty-five adolescent mother–infant pairs were evaluated at postpartum. Maternal and infant body composition was assessed using dual-energy X-ray absorptiometry. Leptin, adiponectin, and ghrelin were measured in maternal circulation and human milk. Multiple linear regression models adjusted for days postpartum assessed associations between (1) maternal characteristics and hormones in maternal blood and milk and (2) milk hormones and infant measures (also adjusted for birth weight).</p> Results <p>Serum and human milk leptin were directly associated (r = 0.472; <i>p</i> = 0.014), whereas serum and human milk ghrelin were inversely correlated (r = −0.320; <i>p</i> = 0.017). Greater maternal fat mass, particularly in the arms and android region, was associated with higher leptin concentrations in serum (β = 5.95; 95% CI: 1.65–10.3 and β = 5.90; 95% CI: 0.871–10.9, respectively) and milk (β = 0.294; 95% CI: 0.132-0.455 and β = 0.280; 95% CI: 0.118–0.443, respectively). Higher milk leptin was associated with lower infant length (β = -1.21; 95% CI: −2.24, −0.183). Milk ghrelin was weakly and inversely associated with several infant anthropometric measures, whereas no significant associations were found for milk adiponectin.</p> Conclusion <p>The results suggest that maternal leptin in serum and milk, but not ghrelin or adiponectin, is associated with maternal adiposity. Leptin and ghrelin in human milk may be involved in infant growth and body composition, whereas adiponectin does not appear to play a major role.</p>