Protein kinase C-θ (PKC-θ) is essential for mature T cell activation; however, the mechanism by which it is recruited to the TCR signaling machinery is unknown. Here we show that T cell stimulation by antibodies or peptide–major histocompatibility complex (MHC) induces translocation of PKC-θ to membrane lipid rafts, which localize to the immunological synapse. Raft translocation was mediated by the PKC-θ regulatory domain and required Lck but not ZAP-70. In addition, PKC-θ was associated with Lck in the rafts. An isolated PKC-θ catalytic fragment did not partition into rafts or activate the transcription factor NF-κB, although addition of a Lck-derived raft-localization sequence restored these functions. Thus, physiological T cell activation translocates PKC-θ to rafts, which localize to the T cell synapse; this PKC-θ translocation is important for its function.