Cancer remains one of the leading causes of death worldwide. New treatments like immunotherapy-especially checkpoint inhibitors and CAR-T cell therapy-have improved outcomes for some patients. However, these therapies often struggle to treat solid tumours effectively. Natural killer (NK) cells are part of the immune system and can naturally detect and destroy cancer cells without previous adaption. Scientists are now enhancing these cells by adding special receptors, called CARs (chimeric antigen receptors), to help them better recognize and attack cancer, an approach originally developed for T cells. CAR-NK cell therapy has some advantages over CAR-T therapy. It tends to cause fewer severe side effects, such as strong immune reactions or off-target effects in healthy tissues. Within some limitations, the allogenic use of CAR-NK cells is possible, as these cells exert less graft-versus-host activity. Such CAR-NK cell products can be produced in larger quantities and stored, making treatment more accessible. Still, there are challenges. It can be difficult to create enough modified NK cells, and the tumour microenvironment can block their activity. This review highlights recent progress in CAR-NK therapy, including early lab and clinical research. It also explores ways to improve these treatments and how they might work alongside other cancer therapies to help more patients in the future.