Introduction <p>While the triglyceride-glucose (TyG) index is a recognized marker of cardiometabolic risk, its influence on blood pressure through body composition in children has not been fully elucidated.</p> Aim <p>This study aimed to investigate the associations between the TyG index and blood pressure in children and adolescents, and to examine the mediating role of body composition in this relationship.</p> Methods <p>A cross-sectional analysis was conducted using data from 408 children aged 6–17&#xa0;years in Guangdong Province, representing a subsample of the National Nutrition and Health Systematic Survey for children aged 0–18&#xa0;years in China. The participants underwent venous blood tests (TyG index calculation), body composition assessments (InBody 770 bioelectrical impedance analyzer), and blood pressure measurements. Linear/logistic regression and mediation analyses were performed to evaluate associations and mediating effects.</p> Results <p>The TyG index showed the strongest positive associations with systolic blood pressure (SBP: β = 4.49, 95% CI 2.36–6.61; <i>P</i>&lt;0.001) and diastolic blood pressure (DBP: β = 2.07, 95% CI 0.56–3.58; <i>P</i>=0.007). Elevated blood pressure risk was significantly linked to the TyG index (OR = 2.04, 95% CI 1.29–3.22; <i>P</i>=0.002) and obesity-related parameters, particularly the fat mass index (FMI: OR = 1.50) and waist‒hip ratio (WHR-z: OR = 2.10). Mediation analysis revealed partial indirect effects of body composition on the TyG-SBP association (total effect: 4.49, 95% CI 2.36–6.61) but no mediation effect for the TyG-DBP.</p> Conclusions <p>Our findings demonstrate that the TyG index is independently associated with elevated blood pressure in children and adolescents. Importantly, obesity-related body fat composition, especially measured by the FMI and WHR, partially mediates the association between TyG index and SBP.</p> Graphical Abstract <p></p>