By late 2018, 2 chimeric antigen receptor T (CAR T) cell products have been approved by US and European regulatory authorities. Tisagenlecleucel (Kymriah, Novartis) is indicated in the treatment of patients up to 25 years of age with B‐cell acute lymphoblastic leukemia (ALL) that is refractory or in second or later relapse, or adult patients with large B‐cell lymphoma relapsed or refractory (r/r) after 2 or more lines of systemic therapy, including diffuse large B‐cell lymphoma (DLBCL) not otherwise specified, high grade B‐cell lymphoma and DLBCL arising from follicular lymphoma. Axicabtagene ciloleucel (Yescarta, Kite) is indicated for the treatment of adult patients with large B‐cell lymphoma relapsed or refractory after 2 or more lines of systemic therapy, including DLBCL not otherwise specified, primary mediastinal large B‐cell lymphoma, high grade B‐cell lymphoma, and DLBCL arising from follicular lymphoma (ZUMA‐1 trial). This review will offer a practical guide for the recognition and management of the most important toxicities related to the use of the current commercial CAR T cells, and also highlight strategies to diminish these side effects in the future.