Purpose: We aimed to study the relationship between thrombocytosis and clinical features of gastric cancerfocussing on platelet counts and gastric cancer progression through different TNM stages. Methods: According to the normal range of platelet count in our institution, 1,596 patients were divided to two groups: a thrombocytosis group (120 patients, > $400{ imes}1000/{mu}L$) and a control group (1,476 patients, ${leq}400{ imes}1000/{mu}L$). Results: The incidence of thrombocytosis was 7.5%. Higher platelet counts were observed in patients with older age, larger tumor size, deeper invasion, lymph node metastasis, distant metastasis and advanced TNM stage. In multivariate logistic regression, tumor size, depth of tumor invasion, lymph node metastasis and TNM stage were independent risk factors for thrombocytosis of gastric cancer patients. On prognostic analysis, age, tumor size, tumor location, histologic type, depth of tumor invasion, lymph node metastasis, distant metastasis and TNM stage and platelet count were important factors. Tumor size, invasion depth, lymph node metastasis, TNM stage and the platelet count were independent prognostic factors. Conclusion: Thrombocytosis is associated with clinical features of gastric cancer patients and correlates with a poor prognosis.