Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease characterized by excessive fibroblast activation and irreversible extracellular matrix deposition. In this study, we developed a lung-targeted stem cell–microsphere hybrid delivery system to enhance the therapeutic efficacy of rapamycin for pulmonary fibrosis. Rapamycin-loaded PLGA microspheres (RAP-MS) were fabricated and conjugated onto the surface of umbilical cord blood–derived mesenchymal stem cells (UCB-MSCs), generating a hybrid therapeutic platform (UCB-RAP). The conjugation of RAP-MS to the stem cell surface was confirmed with stable attachment and preserved cell viability. The hybrid system demonstrated enhanced antifibrotic activity compared with RAP-MS alone in vitro. In vivo biodistribution and pharmacokinetic analyses using IVIS imaging and LC-MS/MS revealed that UCB-RAP exhibited significantly improved lung targeting compared with RAP-MS. In a bleomycin-induced pulmonary fibrosis mouse model, UCB-RAP treatment attenuated fibrotic progression and showed superior therapeutic efficacy compared with RAP-MS or stem cell monotherapy. In addition, therapeutic outcomes were comparable to or better than those achieved with the clinically used antifibrotic drug pirfenidone. These findings suggest that stem cell–microsphere hybrid systems provide an effective strategy for targeted drug delivery and improved treatment of pulmonary fibrosis.