We explored the association between exposure to environmental tobacco smoke (ETS) and various cardiometabolic biomarkers in 10-year-old children. A population-based cross-sectional study was carried out. Data on ETS exposure and potential confounders were collected by parental questionnaire. Adiponectin, leptin, markers of inflammation, apolipoproteins (apo) AI and B, and lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) were measured. Linear and logistic regression models were applied using the 90th percentile as a cut-off point except for adiponectin and apoAI (10th percentile). In linear models, ETS exposure was significantly associated with increasing plasma concentrations of leptin, C-reactive protein, fibrinogen, interleukin (IL)-6, and Lp-PLA(2). When compared with none, ETS exposure of more than 10 cigarettes per day was associated with elevated concentrations of leptin (OR 6.40; 95% CI, 2.67-15.39), C-reactive protein (OR 3.17; 95% CI, 1.31-7.68), Lp-PLA(2) (OR 2.97 95% CI, 1.32-6.68), low adiponectin (OR 2.69; 95% CI, 1.10-6.57), and low apoAI (OR 4.48; 95% CI, 2.16-10.85). Increasing dose of ETS exposure was related to an increasing number of abnormal cardiometabolic markers. Among children, ETS exposure was associated with a low-grade inflammatory response and altered markers of lipid metabolism, which may initiate atherosclerosis in early life. However, longitudinal studies are necessary to determine the potential causal relevance of these associations.