Updated project metadata. Adoptive transfer of chimeric antigen receptor (CAR)-T cells is expected to become the first line of treatment for multiple malignancies, following the enormous success of anti-CD19 therapies. However, their mechanism of action is not fully understood, and clear guidelines for the design of safe and efficient receptors are missing. We hereby describe a systematic analysis of the CAR “signalosome” in human primary T cells. Two CAR designs were compared: a second-generation (PSCA2) and a third-generation (PSCA3) anti-PSCA CAR. Phosphorylation events triggered by CAR-mediated recognition of target cells were quantified by mass spectrometry.