The current meta-analysis analyzed the prognostic impact of elevated platelet count before the treatment of malignant mesothelioma (MM). We performed a search for articles published up to April 15, 2016 in PubMed, MEDLINE, EMBASE, and Web of Science, which evaluated elevated platelet count and survival outcome of MM. STATA version 12 was used for statistical analysis. The pooled hazard ratios (HRs) and their 95% confidence intervals (CIs) were combined to calculate overall effects. The assessment of heterogeneity was tested by the Cochran Q and I² statistics. The sensitivity and meta-regression analyses were performed to explore the origin of heterogeneity. We analyzed 18 eligible studies (3602 patients) that evaluated the correlation between pretreatment platelet count and overall survival (OS). Elevated platelet count was a prognostic factor of poor OS, with a pooled HR of 1.56 (95% CI = 1.36-1.77). However, significant heterogeneity was observed in the included studies (I² = 86.0%, p < 0.001). Sensitivity and meta-regression analyses were performed to trace the origin of heterogeneity. Only the variable type (multivariable or univariate model) was traced as the origin of heterogeneity. Hence, we conducted a subgroup analysis of variable type. The HR was 1.66 (95% CI = 1.41-1.91) in the multivariable group and no significant heterogeneity was observed (I² = 0.0%, p = 0.476). In conclusion, high pretreatment platelet count resulted in poor OS in MM. Therefore, platelet count could be an adequate and useful factor of prognosis for MM.