Objective: The mechanisms underlying the development of peripheral insulin resistance are complex. Several studies have linked sclerostin, an osteocyte-derived inhibitor of the Wnt/β-catenin pathway, to obesity and insulin resistance. The aim of this study was to investigate (1) whether serum sclerostin is associated with insulin sensitivity in lean and/or obese women; and (2) whether hyperinsulinaemia affects serum sclerostin concentrations. Design: A cross-sectional study. Methods: Insulin sensitivity was measured in lean (BMI < 25 kg/m 2 ) and obese (BMI > 30 kg/m 2 ) women using a hyperinsulinaemic–euglycaemic clamp. Serum sclerostin was measured at baseline and during the clamp procedure. Results: We studied 21 lean and 22 obese women with a median age of 40 and 43 years and a median BMI of 22.4 and 33.5 kg/m 2, respectively. Obese women had higher serum sclerostin than lean women (122 ± 33 vs 93 ± 33 nmol/L, P < 0.01). Higher serum sclerostin was associated with lower insulin sensitivity in obese, but not in lean individuals (difference in M-value between highest and lowest quartile: −7.02 mg/kg/min, P = 0.03 and 1.59 mg/kg/min, P = 0.50, respectively). Hyperinsulinaemia did not affect serum sclerostin in lean nor obese women (P >0.5). Conclusion: Serum sclerostin is negatively associated with insulin sensitivity as measured with the hyperinsulinaemic–euglycaemic clamp in obese, but not lean women. This indicates a potential role of the Wnt/β-catenin pathway in regulating insulin sensitivity particularly in obese individuals. Our findings remain hypothesis-generating and should be confirmed by additional studies.