Dickkopf-3 (Dkk-3) may act as a tumor suppressor as it is downregulated in various types of cancer. Moreover, a putative role in tumor neovascularization is discussed. Here, we investigated the expression of Dkk-3 protein in gastric cancer and its potential value as a prognostic marker. Dkk-3 expression was analyzed by immunohistochemistry in 136 tumor samples and was correlated with microvessel density (MVD), tumor stage, and grading as well as the clinical outcome of the patients. Dkk-3 expression was detected in endothelial cells of the tumor vessels in 129/136 (94.9%) and in tumor cells in 85/136 (62.5%) samples. MVD was high and low in 57 (42.9%) and 76 (57.1%) specimens respectively. In tumor cells, overexpression of Dkk-3 was found in 41 (30.1%) of all cases and was correlated significantly to pT-stage (p < 0.05) and UICC stage (p < 0.05). Survival analysis regarding Dkk-3 expression in tumor endothelial cells showed that Dkk-3 is an independent predictor of disease-free survival (p < 0.05). Dkk-3 expression in tumor vessels of patients with gastric cancer identifies a population of patients with relatively favorable prognosis.