Sclerostin and dickkopf-1(DKK1) are Wnt/β-catenin signal antagonists that play an important role in bone formation. Ossification of the posterior longitudinal ligament (OPLL) of the spine is characterized by pathological ectopic ossification of the posterior longitudinal ligament and ankylosing spinal hyperostosis. The aims of this study were to evaluate serum sclerostin and DKK1 levels in persons with OPLL and to identify its relationship with bone metabolism and bone mass in persons with OPLL. This was a case-control study, and 78 patients with OPLL were compared with 39 age- and sex-matched volunteers without OPLL. We analyzed the relationship with calciotropic hormones, bone turnover markers, OPLL localization, number of ossified vertebrae, and bone mineral density of total hip (TH-BMD). Serum sclerostin levels in men with OPLL were significantly higher than in men in the control group (control group: mean = 45.3 pmol/L; OPLL group: mean = 75.7 pmol/L; P = 0.002). Age and sclerostin levels were positively correlated in men with OPLL (r = 0.43; P = 0.002). Serum sclerostin levels in men with OPLL had a positive correlation with TH-BMD Z-score (r = 0.511; P = 0.011, n = 30). There was a strong negative correlation between serum sclerostin levels and serum DKK1 levels in men with OPLL (r = -0.506; P < 0.001). Bone and mineral metabolism in OPLL differs between men and women. In men with OPLL, systemic secretion of sclerostin increases with advancing age and with higher bone mass. These two Wnt/β-catenin signal antagonists have the opposite effect in persons with OPLL, and higher serum sclerostin levels are counterbalanced by underproduction of DKK1.