Due to the molecular complexity of cancer, combination therapy is becoming increasingly important for better long-term prognosis with fewer side effects. To further increase the therapeutic effects, advanced drug delivery systems (DDSs), capable of simultaneously delivering multiple drugs to the site of action with specific time-programmed release profiles, are important requirements. Nanocarriers for the simultaneous co-delivery of multiple chemical drugs in combination therapy have been extensively reviewed. Here we focus on the nanotechnology enabled DDSs for the simultaneous co-delivery of therapeutic genes and chemical drugs for cancer treatment. The opportunities for this combination strategy and their challenges will be discussed.