Telomere length is considered a biomarker of biological aging. Shorter telomeres and obesity have both been associated with age-related diseases. To evaluate the association between various indices of obesity with leukocyte telomere length (LTL) in childhood, data from 1,396 mother-child pairs of the multi-centre European birth cohort study HELIX were used. Maternal pre-pregnancy body mass index (BMI) and 4 adiposity markers in children at age 8 (6–11) years were assessed: BMI, fat mass, waist circumference, and skinfold thickness. Relative LTL was obtained. Associations of LTL with each adiposity marker were calculated using linear mixed models with a random cohort effect. For each 1 kg/m² increment in maternal pre-pregnancy BMI, the child’s LTL was 0.23% shorter (95%CI: 0.01,0.46%). Each unit increase in child BMI z-score was associated with 1.21% (95%CI: 0.30,2.11%) shorter LTL. Inverse associations were observed between waist circumference and LTL (−0.96% per z-score unit; 95%CI: −2.06,0.16%), and skinfold thickness and LTL (−0.10% per z-score unit; 95%CI: −0.23,0.02%). In conclusion, this large multicentric study suggests that higher child adiposity indicators are associated with short telomeres in children, and that associations are stronger for child BMI than for maternal pre-pregnancy BMI.