The present invention provides a universal, yet adaptable, anti-tag chimeric antigen receptor (AT-CAR) system which provides T cells with the ability and specificity to recognize and kill target cells, such as tumor cells, that have been marked by tagged antibodies. As an example, αFITC-CAR-expressing T cells have been developed that specifically recognize various human cancer cells when those cells are bound by cancer-reactive FITC-labeled antibodies. The activation of αFITC-CAR-expressing T cells is shown to induce efficient target lysis, T cell proliferation, and cytokine/chemokine production. The system can be used to treating subjects having cancer.