Abstract: The main objective in gene delivery system is the development of efficient, non-toxic gene carriers that can encapsulate and deliver foreign genetic materials into specific cell types To perform gene transfer two types of vectors are available, (i) viral vectors (ii) nonviral vectors. Among the vectors, nonviral vectors are proved less toxic and safe compare to viral vectors through clinical trial. No single vector is proved suitable for every gene transfection experiment. Cationic polymers such as polyethylenimine (PEI) and poly L-lysine (PLL) and their complexes are experimentally established as non-viral vector with higher transfection efficiency. Identifying the barriers for transfection and the possible solution, the stability improvement research is needed for better clinical performance of cationic polymers. In future it is also possible to find new conjugates as cationic polymers bearing many properties, suitable to bound with DNA and penetrate cell. Considering all these properties, these works reviews the most recent studies highlighting cationic polymers used in nonviral gene delivery systems.