Osteosarcoma is the most common malignant bone tumor that occurs in children and adolescents. Various studies have investigated the role of serum alkaline phosphatase (ALP) level in patients with osteosarcoma but report conflicting findings. Thus, a meta-analysis to assess its prognostic value more precisely is conducted. Pooled hazard ratio (HR) with 95% confidence intervals (CIs) of overall survival (OS) was used to assess the prognostic role of serum ALP level. Eleven studies published between 1993 and 2013 with a total of 1336 osteosarcoma patients were included. Overall, the pooled HR for all 11 eligible studies evaluating high ALP level on OS was 1.60 (95% CI: 1.38-1.86). Sensitivity analysis suggested that the pooled HR was stable and omitting a single study did not change the significance of the pooled HR. Begg's (0.553) and Egger's (0.382) test also did not suggest evidence for publication bias. This meta-analysis suggests that high serum ALP level is obviously associated with lower OS rate in patients with osteosarcoma, and it is an effective biomarker of prognosis.