The aim of the present meta-analysis study was to determine the association between pre-treatment thrombocytosis and prognosis of patients with endometrial cancer. Articles published prior to December 2018 containing information on platelet count and endometrial cancer were searched in the PubMed, Embase and the Cochrane Library databases. A platelet count of ≥350 or >400×10/l was considered to indicate thrombocytosis. Hazard ratios (HRs) with 95% CI were calculated using a random- or fixed-effects model to assess the strength of the associations. A Funnel plot and Egger's test were used to evaluate the publication bias and sensitivity analyses were performed to estimate the robustness of the present results by using Stata 13.0 software. A pooled analysis of 11 studies that met the inclusion criteria was performed, involving a total of 2,590 patients with endometrial cancer. The overall survival (OS), progression-free survival (PFS) and disease-free survival (DFS) time of patients with endometrial cancer who exhibited pre-treatment thrombocytosis were shorter than those in patients without pre-treatment thrombocytosis (OS, HR=2.25, 95% CI=1.26-4.00; PFS, HR=2.60, 95% CI=1.23-5.50; DFS, HR=2.23, 95% CI=1.45-3.42). However, pre-treatment thrombocytosis was not associated with disease-specific survival time in patients with endometrial cancer (HR=2.17, 95% CI=0.51-9.27; P=0.296). Subgroup analysis indicated that pre-treatment thrombocytosis was not associated with OS time in patients of Asian and European ethnicity. Furthermore, pre-treatment thrombocytosis (platelet count >400×10/l) was an independent predictor of OS, PFS and DFS regardless of the clinical stage.