The impact of phenotypic, clonal, and functional heterogeneity of chimeric antigen receptor (CAR)-T cells on clinical outcome remains understudied. Here, we integrate clonal kinetics with transcriptomic heterogeneity resolved by single-cell omics to interrogate cellular dynamics of non-transduced (CAR) and transduced (CAR) T cells, in the infusion product (IP) and at the CAR-T cell expansion peak in five B cell acute lymphoblastic leukemia (B-ALL) patients treated with CD19CAR-T cells (varni-cel). We identify significant differences in cellular dynamics in response to therapy. CAR T cells at IP of complete response patients exhibit a significantly higher CD4:CD8 ratio, validated in a larger cohort B-ALL patients (n = 47). Conversely, at the expansion peak, there is a clonal expansion of CD8 effector memory and cytotoxic T cells. Cytotoxic CAR γδ-T cells expansion correlates with treatment efficacy validated in a cohort of B-ALL (n = 18) and diffuse large B cell lymphoma (DLBCL) patients (n = 58). Our data provide insights into the complexity of T cell responses following CAR-T cell therapy and suggest drivers of immunotherapy response.