PURPOSE: This study aimed to investigate the molecular mechanism underlying diffuse large B-cell lymphoma (DLBCL). METHODS: Serum miRNA expression analysis for the serum samples of patients with DLBCL and those of controls was performed using the Illumina sequencing technology. Differentially expressed miRNAs (DEMs) were identified on the basis of the sequencing data. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses and protein-protein interaction (PPI) network construction for the target genes of DEMs were also conducted. Moreover, the selected DEMs were verified using real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR). RESULTS: Fifty-one DEMs were identified between DLBCL disease and control groups, of which two were upregulated and 49 were downregulated. In total, 3631 target genes of DEMs were obtained, and hsa-miR-34a-5p had the most target genes. Among the 51 DEMs, 19 were significantly enriched in 41 KEGG pathways. hsa-miR-34a-5p was enriched in 15 pathways such as the p53 signaling pathway. hsa-miR-323b-3p was enriched in four pathways such as pathways in cancer. The PPI network revealed that hsa-miR-34a-5p had the most target genes such as tumor protein p53 (TP53), and hsa-miR-431-5p regulated tyrosine protein kinase Fyn (FYN). Furthermore, qRT-PCR results showed that hsa-miR-34a-5p was upregulated, whereas hsa-miR-323b-3p and hsa-miR-431-5p were downregulated. CONCLUSION: hsa-miR-34a-5p may be directly regulated by TP53 and may be involved in DLBCL development via the p53 signaling pathway. Furthermore, hsa-miR-323b-3p may be related to DLBCL by participating in pathways in cancer. hsa-miR-431-5p may also play a role in DLBCL by regulating FYN.