Cell mediated drug delivery is explored widely to target drugs to particular organs (e.g., spleen, lungs etc.) in cancer, tissue inflammation or in bone injury. The highly mobile cells like mononuclear phagocytes (dendritic cells, Sertoli cells, monocytes and macrophages), neutrophils and lymphocytes loaded drug nanocarriers are exploited as trojan horses for drug delivery. Cell mediated drug delivery systems serve as biocompatible and less toxic drug delivery approach. Formulation of cell-based drug delivery is different than that of conventional drug delivery systems, the former has more formulation challenges. Nevertheless, multifunctional cell system opens new perspectives for the active delivery of drugs to the target site. Single cell assay plays potential role in identifying cellular target for nanoparticles and for cell-based drug delivery.