The use of a drug delivery system (DDS) represents a novel therapeutic approach in the treatment of multiple myeloma in bone lesion. We show the immunomodulatory effects of anionic and cationic dendritic poly(ethyleneimine) glycoarchitectures (PEI-DGAs) on human myeloma cell lines and cells in their microenvironment, in vitro differentiated macrophages, and mesenchymal stromal cells (MSCs). PEI-DGAs do not influence the secretion of IL-6, which is a major growth and survival factor in multiple myeloma. Cationic PEI-DGAs in turn have cytostatic properties on multiple myeloma cell lines. Anionic PEI-DGAs induce the secretion of proinflammatory cytokines IL-1β, TNFα, and IL-6 in macrophages and MSCs, whereas cationic PEI-DGAs do not. Macrophages and MSCs show remarkably high cell viability in the presence of high concentration of PEI-DGAs. RNA sequencing of MSCs exposed to cationic PEI-DGAs supports the hypothesis that smaller cationic PEI-DGAs are less toxic and could improve osteogenic differentiation in an ideal DDS.