This review article discusses the potential and challenges of chimeric antigen receptor (CAR) T cells and CAR natural killer (CAR-NK) cells as cellular cancer immunotherapies, particularly for solid tumors. CAR-T cell therapy has shown remarkable efficacy in hematological malignancies, but its application in solid tumors remains limited due to obstacles such as poor tumor trafficking, infiltration, and an immuno-suppressive tumor microenvironment (TME). CAR-NK cells offer several advantages over CAR-T cells, including HLA-independence and the potential for "off-the-shelf" therapeutics. However, they also face challenges such as short half-life and short-term anti-cancer activity. The article highlights recent advances in engineering strategies to improve the efficacy of both CAR-T and CAR-NK cells, including multi-targeting, enhanced trafficking, and modulation of the TME. Additionally, it explores the use of immunostimulatory signals and genetic regulators to enhance CAR-T cell function and reduce side effects. For CAR-NK cells, strategies to increase trafficking, overcome TME immunosuppression, and enhance persistency are discussed. The review concludes by emphasizing the importance of continued research to optimize these cellular immunotherapies for solid tumors.This review article discusses the potential and challenges of chimeric antigen receptor (CAR) T cells and CAR natural killer (CAR-NK) cells as cellular cancer immunotherapies, particularly for solid tumors. CAR-T cell therapy has shown remarkable efficacy in hematological malignancies, but its application in solid tumors remains limited due to obstacles such as poor tumor trafficking, infiltration, and an immuno-suppressive tumor microenvironment (TME). CAR-NK cells offer several advantages over CAR-T cells, including HLA-independence and the potential for "off-the-shelf" therapeutics. However, they also face challenges such as short half-life and short-term anti-cancer activity. The article highlights recent advances in engineering strategies to improve the efficacy of both CAR-T and CAR-NK cells, including multi-targeting, enhanced trafficking, and modulation of the TME. Additionally, it explores the use of immunostimulatory signals and genetic regulators to enhance CAR-T cell function and reduce side effects. For CAR-NK cells, strategies to increase trafficking, overcome TME immunosuppression, and enhance persistency are discussed. The review concludes by emphasizing the importance of continued research to optimize these cellular immunotherapies for solid tumors.