Binding of the T cell receptor (TCR) to peptide-major histocompatibility complex (pMHC) initiates signaling leading to T cell activation. Signaling is proposed to be triggered by the segregation of the transmembrane phosphatase CD45 from TCR-pMHC, caused by a difference in sizes of their extracellular domains. Here, we have reconstituted the segregation of CD45 from TCR-pMHC using purified proteins on model membranes. Similar to the sensitivity of T cell signaling, TCR-pMHC interactions with Kds of <15 μM were needed to exclude CD45; the larger of two developmentally-regulated isoforms of CD45 was excluded more rapidly and efficiently. We further show that two receptor-ligand pairs, TCR-pMHC and the inhibitory co-receptor PD-1 with its ligand PD-L1, segregate from one another and together create zones of CD45 exclusion. These results demonstrate that the binding energy of TCR-pMHC at membrane-membrane interfaces is sufficient to create spatial partitioning of the TCR relative to CD45.