The remarkable success of mRNA‐based coronavirus 2019 (COVID‐19) vaccines has propelled the advancement of nanomedicine, specifically in the realm of RNA technology and nanomaterial delivery systems. Notably, significant strides have been made in the development of RNA‐based in vivo chimeric antigen receptor (CAR) therapy. In comparison to the conventional ex vivo CAR therapy, in vivo CAR therapy offers several benefits including simplified preparation, reduced costs, broad applicability and decreased potential for carcinogenic effects. This review summarises the RNA‐based CAR constructs in in vivo CAR therapy, discusses the current applications of in vivo delivery vectors and outlines the immune cells edited with CAR molecules. We aim for the conveyed messages to contribute towards the advancement of in vivo CAR application.