Background: Evidence indicates that Dickkopf-1 (DKK-1) levels may be a biomarker for cancer risk. The aim of this study was to assess DKK-1 and its correlation with clinic-pathological features in patients with bladder cancer. Materials and Methods: DKK-1 levels were determined in serum samples from 90 patients with bladder cancer before transurethral tumor resection. The concentrations of DKK-1 were determined by using enzyme linked immune-sorbent assay (ELISA). Results: Elevated preoperative DKK-1 levels were associated with tumor stage (p<0.001), grade (p<0.001) and histological grade (p<0.001). Conclusions: The results of our study demonstrated that the level of serum DKK-1 is correlated with both disease progression and increase in the tumor grade. Preoperative serum DKK-1 elevation may thus represent a novel marker for the determination of bladder cancer and the detection of patients with a likely poor clinical outcome.