BACKGROUND: Growth trajectories have shown to be related to obesity and metabolic risks in later life, however body mass index (BMI) trajectories according to the presence or absence of metabolic syndrome (MS) and its parameters in adulthood are scarce in literature. OBJECTIVES: To investigate BMI trajectories during childhood in relation to MS and its parameters in adult age. METHODS: A total of 1919 subjects (43.4% male, 20-60 y) participated in this retrospective cohort study. Height, weight, waist circumference (WC), blood glucose, high-density lipoprotein cholesterol, triglycerides and blood pressure were measured at adulthood. Childhood weight and height were collected retrospectively from health booklets. Differences between BMI growth curves of subjects with and without MS were assessed using mixed models for correlated data. RESULTS: BMI trajectories differed according to the presence or not of MS at adulthood, from the age of 4 years forward (all P < 0.05), to the presence or not of hypertriglyceridemia from 1.5 years forward (all P < 0.05), and to WC > 94 cm (men) / 80 cm (women) compared to lower WC, at all ages (all P<0.05). CONCLUSIONS: BMI growth curves differ according to the presence or not of MS at adulthood, but differences only appeared after the age of 4 years. Changes vary according to the MS parameters considered. Deviation of the MS-associated BMI curve from normal pattern could correspond to alteration in body composition. These differences in BMI trajectories during childhood support the theory of an early origin of the MS, justifying early prevention.