The Wnt/β‐catenin pathway is a major signaling cascade in bone biology, playing a key role in regulating bone development and remodeling, with aberrations in signaling resulting in disturbances in bone mass. The objectives of our study were to correlate serum Dkk1 expression with bone mineral density (BMD) and assess the potential role of Dkk1 as a serological marker of bone mass. Serum was collected from a cohort of patients (n = 36), 18 patients with a reduced BMD and 18 control patients. Serum Dkk1 expression as quantified by ELISA was correlated with lumbar and femoral t‐ and z‐scores. Serum Dkk1 concentration in the osteoporosis group was significantly higher than control group (941 ± 116 vs. 558 ± 47 pg/ml, p < 0.01). Serum Dkk1 expression was highly correlated with bone mass variables with inverse associations found between serum Dkk1 expression and lumbar t‐score (r = −0.34, p = 0.00433), lumbar z‐score (r = −0.22, p = 0.1907), femur t‐score (r = −0.42, p = 0.0101), and femur z‐score (r = −0.43, p = 0.0089). Our data further emphasizes the pivotal role played by Wnt/β‐catenin signaling in bone mass regulation. Dkk1, a powerful antagonist of canonical Wnt signaling, may have a role to play as a serological marker for disorders of bone mass, warranting further evaluation. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:414–418, 2011