The present invention relates to the generation of chimeric antigen receptors (CAR) referred to as multi-chain CARs. Such CARs, which aim to redirect immune cell specificity and reactivity toward a selected target exploiting the ligand-binding domain properties, comprise separate extracellular ligand binding and signaling domains in different transmembrane polypeptides. The signaling domains are designed to assemble in juxtamembrane position, which forms flexible architecture closer to natural receptors, that confers optimal signal transduction. The invention encompasses the polynucleotides, vectors encoding said multi- chain CAR and the isolated cells expressing them at their surface, in particularly for their use in immunotherapy. The invention opens the way to efficient adoptive immunotherapy strategies for treating cancer and viral infections.