TCR binding to its ligands induces a cascade of signaling starting by the phosphorylation of immunoreceptor tyrosine-based activation motif (ITAMs) present in the TCR-associated CD3 complex. This is followed by the phosphorylation of proteins including the adaptor LAT, which once phosphorylated interacts with multiple proteins allowing signal diversification and amplification downstream of the TCR. We take advantage of peroxidase-catalyzed proximity labeling combined with quantitative mass spectrometry to track the formation of CD3z and LAT interactome dynamics in Jurkat cells after TCR stimulation. We find more than 1 000 high confidence proteins for each bait and provide a quantitative molecular map of proteins enriched or reduced from the vicinity of CD3z and LAT, after stimulation. We detail and compare the recruitment kinetics of signaling proteins to CD3z and LAT and identify previously uncharacterized mediators of T cell activation. We show that the kinase MARK2, which is in the proximity of LAT and CD3z at resting state and lost upon activation, is a negative regulator of cytokine production by T cells. This study provides a resource for uncovering the complex signaling networks that regulate TCR activation and highlights new players of the TCR-induced signaling cascade.