CAR-T and CAR-NK cells are promising cellular immunotherapies for cancer treatment. CAR-T cells have shown success in hematological malignancies but face challenges in solid tumors due to limited tumor infiltration and an immunosuppressive tumor microenvironment (TME). CAR-NK cells offer advantages such as no HLA compatibility requirements and the potential for "off-the-shelf" therapies. However, both CAR-T and CAR-NK cells face challenges in solid tumors, including tumor heterogeneity, infiltration barriers, and immunosuppressive TME. Recent advances in engineering strategies aim to improve CAR-T and CAR-NK cell therapies by enhancing antigen targeting, increasing trafficking and infiltration into tumors, and blocking inhibitory signals. Strategies include modifying CARs with co-stimulatory domains, engineering CAR-T cells to secrete cytokines, and using gene editing to enhance NK cell function. CAR-NK cells also face challenges in solid tumors, including limited infiltration and immunosuppressive TME. Strategies to improve CAR-NK cell therapy include enhancing NK cell trafficking, overcoming TME immunosuppression, and optimizing CAR design for NK cells. These advancements highlight the potential of CAR-T and CAR-NK cell therapies in the treatment of solid tumors.CAR-T and CAR-NK cells are promising cellular immunotherapies for cancer treatment. CAR-T cells have shown success in hematological malignancies but face challenges in solid tumors due to limited tumor infiltration and an immunosuppressive tumor microenvironment (TME). CAR-NK cells offer advantages such as no HLA compatibility requirements and the potential for "off-the-shelf" therapies. However, both CAR-T and CAR-NK cells face challenges in solid tumors, including tumor heterogeneity, infiltration barriers, and immunosuppressive TME. Recent advances in engineering strategies aim to improve CAR-T and CAR-NK cell therapies by enhancing antigen targeting, increasing trafficking and infiltration into tumors, and blocking inhibitory signals. Strategies include modifying CARs with co-stimulatory domains, engineering CAR-T cells to secrete cytokines, and using gene editing to enhance NK cell function. CAR-NK cells also face challenges in solid tumors, including limited infiltration and immunosuppressive TME. Strategies to improve CAR-NK cell therapy include enhancing NK cell trafficking, overcoming TME immunosuppression, and optimizing CAR design for NK cells. These advancements highlight the potential of CAR-T and CAR-NK cell therapies in the treatment of solid tumors.