Background <p>To explore the effect and mechanism of pomalidomide on the immune activity of dendritic cell-derived exosomes (DEXs) from patients with multiple myeloma (MM).</p> Methods <p>MoDCs were induced from monocytes obtained from patients with MM and HDs with or without pomalidomide treatment. DEXs were then isolated from culture supernatants via ultracentrifugation and characterized by TEM and NTA. Surface markers (CD63, CD81, CD80, CD86, and HLA-DR) were analyzed using nanoflow cytometry. Functional assays included coculturing DEXs with autologous PBMCs to activate T cells, followed by sorting CD8⁺ T cells and assessing their pro-apoptotic effect on U266 cells via flow cytometry. Mechanistic insights were explored through miRNA sequencing of DEXs and transcriptome sequencing of T cells.</p> Results <p>Pomalidomide significantly increased the proportion of DEXs derived from patients with multiple myeloma (MM) and increased the expression levels and mean fluorescence intensity (MFI) of surface activation markers, including CD80, CD86 and HLA-DR. Functional assays demonstrated that DEXs treated with pomalidomide promoted the generation of CD8⁺ T cells and markedly increased both early and total apoptosis rates in U266 cells. Mechanistically, miRNAomic analysis indicated that pomalidomide potentially facilitates T-cell activation by modulating signaling pathways such as the MAPK and PI3K-Akt pathways. Transcriptome profiling further verified that this treatment triggered substantial metabolic reprogramming in T cells and significantly activated pathways associated with T-cell activation.</p> Conclusions <p>This study provides a new strategy for enhancing the activity of DEXs derived from patients with MM, with the potential to develop DEXs as an antitumor vaccine for MM.</p>