OBJECTIVE:To explore associations of perinatal and family factors with preadolescence overweight and obesity in a sample of Greek schoolchildren. METHODS:A nationwide cross-sectional study among 2093 students (10.9 ± 0.72 years, 44.9% boys) and their parents were conducted. Anthropometric (e.g., height, weight, mother's body mass index (BMI) at the time of the study and at conception), socio-demographic (e.g., age, education, socio-economic status), diet and other major lifestyle characteristics (e.g., smoking, alcohol intake, physical activity and inactivity) and perinatal factors (e.g., breast- and formula-feeding) were collected with validated questionnaires. Height and weight of students were measured. Overweight/obesity was classified using IOTF cut-offs. Multivariable logistic and linear regression analyses were used to identify major independent factors of overweight/obesity among preadolescents and factors related with the percentage change of mother's BMI, respectively. RESULTS:Increased age at pregnancy [odds ratios (OR)=0.95, 95% Confidence Interval (CI): 0.93-0.97], higher BMI at conception (OR=1.17, 95% CI: 1.12-1.22) and heavy smoking (OR = 2.02, 95% CI: 1.23-3.33) were positively associated with child's overweight/obesity status. Moreover, mother's age and TV viewing, indicating inactivity, were the strongest factors of the percentage increase in mother's BMI (b ± se = 0.23 ± 0.07, p = 0.002; b ± se=0.32 ± 0.10, p = 0.002, respectively). CONCLUSIONS:Preadolescent obesity is associated with mother's pre-pregnancy weight, age and heavy smoking at conception and mother's BMI change after gestation.