Cationic polymers have been increasingly proposed as potential gene delivery vectors because of their versatility. In this paper, we focus on the characteristics of poly(ester amine)s (PEAs) as gene delivery carriers, degradation pattern as an essential parameter for reduced toxicity, classification based on its physicochemical properties followed by its success as efficient gene delivery carrier in vitro and in vivo. We also discuss the conjugation of ligands/charged groups to the side chain of the polyester in order to achieve receptor-mediated endocytosis as well as target-specific delivery of DNA. Capable of delivering exogenous genes to a cell nucleus, these cationic PEAs also serve as a valuable model to understand the important characteristics that render a polymer an effective gene carrier.