Background/Aims: Serum 25-hydroxyvitamin D [25(OH)D] levels proved to be associated with prognosis of patients with colorectal cancer or breast cancer, but its prognostic role in hematological malignancies was still unclear. A systematic review and meta-analysis was performed to comprehensively evaluate the association between serum 25(OH)D levels and prognosis of patients with hematological malignancies. Methods: We searched Pubmed, Embase, Web of Science, and Google Scholar for studies evaluating the association between serum 25(OH)D levels and prognosis of patients with hematological malignancies. The hazard ratios (HR) with 95% confidence intervals (95%CI) for overall survival (OS) or relapse-free survival (RFS) were pooled using meta-analysis. Results: Seven studies with a total of 2,643 patients with hematological cancer were finally included into the meta-analysis. Overall, compared with normal serum 25(OH)D levels, low serum 25(OH)D levels were significantly associated with both poorer OS (HR = 1.85, 95% CI 1.54-2.23, P <0.001) and poorer RFS (HR = 1.45, 95% CI 1.25 to 1.70, P <0.001) in hematological malignancies. Subgroup analysis further showed that low serum 25(OH)D levels were significantly associated with poorer OS and RFS in both lymphoma and leukemia. Conclusion: Low serum 25(OH)D levels are significantly associated with poorer prognosis in patients with hematological malignancies including lymphoma and leukemia.