Chemotherapy is among the most common means for clinicians in the fight against various types of tumors. However, severe toxicity with undesirable toxic effects against normal tissues and cells significantly hinders the applications of these chemotherapeutic agents and leads to multiple complications for patients. Recent developments of nanotechnology-enabled drug delivery platforms allow simultaneous delivery of multiple chemotherapeutic agents to target different metabolic pathways of tumor cells, thus providing new opportunities for higher therapeutic efficacy and lower cytotoxicity. Furthermore, multifunctional nanocarriers can also deliver diagnostic agents, including MRI contrast agents and fluorescent probes, to achieve cancer diagnosis and therapy at the same time. This present review discusses the various aspects of current co-delivery strategies and emphasizes the need for novel designs of biocompatible and non or low toxic nanocarriers. Further studies on potential adverse effects of various nanocarriers are warranted.