OBJECTIVE: Investigate associations of TV viewing time and accelerometry-derived sedentary time with inflammatory and endothelial function biomarkers in children. METHODS: Cross-sectional analysis of 164 7-10-year-old children. TV viewing time was assessed by parental proxy report and total and patterns of sedentary time accumulation (e.g. prolonged bouts) were assessed by accelerometry. C-reactive protein (CRP), homeostasis model assessment of insulin resistance, interleukin-2, -6, -8, -10, tumour necrosis factor alpha, adiponectin, resistin, brain-derived neurotrophic factor, soluble intercellular and vascular adhesion molecule 1, plasminogen activator inhibitor 1 and soluble E-selectin were assessed. Generalised linear models assessed the associations of TV viewing and sedentary time with biomarkers, adjusting for sex, waist circumference, moderate- to vigorous-intensity physical activity and diet density. RESULTS: Each additional h week(-1) of TV viewing was associated with 4.4% (95% CI: 2.1, 6.7) greater CRP and 0.6% (0.2, 1.0) greater sVCAM-1 in the fully adjusted model. The association between frequency and duration of 5-10 min bouts of sedentary time and CRP was positive after adjustment for sex and waist circumference but attenuated after adjustment for diet density. CONCLUSIONS: This study suggests that TV viewing was unfavourably associated with several markers of inflammation and endothelial dysfunction. The detrimental association between 5 and 10 min bouts of sedentary time and CRP approached significance, suggesting that further research with a stronger study design (longitudinal and/or experimental) is needed to better understand how the accumulation of sedentary time early in life may influence short and longer term health. © 2015 The Authors. Pediatric Obesity published by John Wiley & Sons Ltd on behalf of World Obesity.