Adiposity contributes to inflammation and oxidative stress in the general population, but this association has not been examined in the chronic kidney disease (CKD) population. We investigated the relationship between body mass index, body fat percentage, and markers of inflammation (C-reactive protein) and oxidative stress (F(2)-isoprostanes and protein thiols) in 184 patients with stages III to IV CKD and 43 healthy controls. We found that, on average, patients with CKD had 62% higher F(2)-isoprostanes, 7% lower protein thiols (a measure of endogenous anti-oxidant capacity, inversely related to protein oxidation), and 150% higher C-reactive protein levels than healthy controls (all unadjusted P < 0.001). In separate multivariable linear regression models, body mass index and body fat percentage each positively correlated with levels of F(2)-isoprostanes and C-reactive protein and negatively correlated with levels of protein thiols among patients with CKD after adjusting for age, sex, race, hypertension, diabetes mellitus, smoking history, estimated glomerular filtration rate, total cholesterol, serum albumin, and study site. We conclude that increased adiposity may amplify the oxidative stress and inflammation that accompany moderate to severe CKD. Interventions focused on weight loss may decrease the inflammatory and oxidative burden in CKD, which may ultimately attenuate cardiovascular risk in this population.