Cationic dendrimers are promising tools in the introduction of nucleic acids into mammalian cells, however, present dendrimer-based gene vectors have modest transfection efficacy and significant toxicity. Here, we synthesized triphenylphosphonium (TPP) conjugated dendrimers and used them as polymeric gene vectors. TPP-conjugated dendrimers can effectively target mitochondria and showed efficient transfection efficacy on HeLa and COS-7 cells with low cytotoxicity on the transfected cells. These materials achieved much higher efficacy than the commercial transfection reagent SuperFect and comparable efficacy with Lipofectamine 2000. This study provides a new insight into the design of efficient and biocompatible gene vectors using dendrimers as scaffolds.