MicroRNAs (miRNAs) are regulatory RNA molecules that are deregulated in many disease types, including cancer. Recently, miRNAs have shown promise as markers for cancer diagnosis. The aim of this study was to investigate whether serum miRNAs can be used as biomarkers for the detection of diffuse large B cell lymphoma (DLBCL). We measured the levels of miRNAs (miR-15a, miR-16-1, miR-21, miR-29c, miR-34a, miR-155, and miR-223) in serum samples from patients with DLBCL and healthy controls using real-time quantitative reverse-transcription polymerase chain reaction (qRT-PCR). We show here that miRNAs are present in human serum in a remarkably stable form. Four of miRNAs (miR-15a, miR-16-1, miR-29c, and miR-155) were significantly elevated in DLBCL serum when compared with normal controls (P < 0.05), while miR-34a was downregulated in DLBCL serum when compared with controls (P < 0.05). Receiver operating characteristic analyses reflects strong discriminating DLBCL from controls, with area under the curves of 0.7722, 0.7002, 0.6672, 0.8538, and 0.7157 for miR-15a, miR-16-1, miR-29c, miR-34a, and miR-155, respectively. At the cut-off value of 0.0006 for miR-15a, the sensitivity was 80% and the specificity was 76%; at the cut-off value of 0.0886 for miR-16-1, the sensitivity was 94% and the specificity was 51%; at the cut-off value of 1.395 for miR-34a, the sensitivity was 100% and the specificity was 70%; at the cut-off value of 0.0022 for miR-155, the sensitivity was 83% and the specificity was 65%. In conclusion, these data suggest that serum miRNAs are potentially useful tools as novel noninvasive biomarker for the diagnosis of DLBCL.