© The Royal Society of Chemistry 2016. For effective gene delivery to breast cancer MCF-7 cells, a folate-targeting redox gene carrier was synthesized by Michael addition polymerization between 1-(2-aminoethyl)piperazine and N,N′-cystaminebisacrylamide. Folate was then conjugated through an amidation reaction. The obtained folate-modified hyperbranched poly(amido amine)s (FA-PAAs) degraded in the presence of glutathione and displayed excellent transfection efficiency in vitro. In particular, FA-PAAs showed much higher gene delivery efficiency than PEI-25k in the presence of serum, leading to an obvious decrease in MMP-9 protein expression and the apoptosis of MCF-7 cells. Moreover, FA-PAAs displayed lower cytotoxicity and better blood compatibility than PEI-25k, suggesting a potential application in gene therapy for tumors.