Upon antigen recognition by the TCR, leukocyte function-associated antigen-1 (LFA-1) physically associates with the leukocyte adhesion molecule DNAM-1 (CD226), for which the serine phosphorylation at residue 329 (S329) of DNAM-1 plays a critical role. The TCR-mediated signal also induces the formation of the immunological synapse (IS), in which lipid raft-associated molecules, including LFA-1, DNAM-1, protein kinase C, Fyn and others, are recruited, resulting in efficient signal transduction for T cell activation. However, the molecular mechanisms of lipid raft recruitment of many associated molecules have remained unclear. Here, we demonstrate that, while both wild-type (WT) and mutant DNAM-1 at S329 were polarized at the IS, the WT, but not mutant, DNAM-1 associated with lipid rafts at the peripheral supra-molecular activation clusters. We also demonstrate that the association of DNAM-1 with lipid rafts was necessary for the tyrosine phosphorylation of DNAM-1, which is essential for LFA-1-mediated co-stimulatory signaling for naive T cell proliferation and differentiation.