Diffuse large B-cell lymphoma (DLBCL) is a heterogeneous group of B-cell lymphomas. Exploring a novel and important biomarker is indispensable for understanding the mechanism and clinical course of DLBCL. Emerging studies have shown that aberrant expression of long noncoding RNA (lncRNAs) is strongly associated with carcinogenesis. The aim of this study was to investigate the value of lncRNA LUNAR1 in DLBCL. Quantitative real-time PCR was performed to illustrate the patterns of LUNAR1 expression in tumor tissues and cell lines. The higher expression of LUNAR1 was significantly correlated with stage, rituximab and IPI. Univariate and multivariate analyses showed that LUNAR1 expression served as an independent predictor for overall survival and progression-free survival. Receiver operating characteristic (ROC) curve was constructed to evaluate the diagnostic values and the area under the ROC curve of LUNAR1 was up to 0.9420. Further experiments revealed that LUNAR1 knockdown significantly repressed cell proliferation of DLBCL by regulating E2F1, cyclin D1 and p21. In conclusion, our results indicate that LUNAR1 may serve as a candidate prognostic biomarker through growth regulation in DLBCL.