Adipose tissue appears to be a modulator of vascular injury and systemic inflammation. The aim of this study was to establish the relationship between plasma adiponectin concentration and severity of proteinuria in patients with proteinuria. We enrolled 77 patients with nephrotic and non-nephrotic proteinuria with normal renal function along with 38 matched controls in a cross-sectional study. These patients were divided into group 1 (n = 44, non-nephrotic proteinuria, <3.5 g/day) and group 2 (n = 43, nephrotic proteinuria, >3.5 g/day) by severity of proteinuria. Circulating adiponectin and high-sensitivity C-reactive protein (hsCRP) levels were measured using commercial ELISA. HOMA index and hsCRP levels were all significantly higher in proteinuric patients than in control subjects, while plasma adiponectin levels were significantly lower (p < 0.001). When compared to patients with non-nephrotic proteinuria, patients with nephrotic proteinuria had significantly higher plasma hsCRP and HOMA index (p < 0.001). According to the multiple regression analysis, proteinuria levels were independently related to adiponectin levels. Decreases in adiponectin levels were more prominent in patients with nephrotic proteinuria than in patients with non-nephrotic proteinuria. These results show that the reduction of plasma adiponectin concentrations depend on insulin resistance and inflammation rather than directly severity of proteinuria in patients with proteinuria.