Clinical efficacy of PD-1/PD-L1 targeting relies upon the reactivation of tumor-specific but functionally impaired PD-1+ T cells present before therapy. Thus, analyzing early stage primary tumors may reveal the presence of T cells that are not yet functionally impaired. In this study, we report that activated (HLA-DR+) T cells with an effector memory (TEM) profile are enriched in such lesions. Tumor-infiltrating lymphocytes (TIL) coexpressed PD-1 with the inhibitory receptors TIM-3, CTLA-4, LAG-3 and TIGIT, but also displayed a recently activated, non-exhausted phenotype. We also identified a subset of CD8+PD-1+FOXP3+ T lymphocytes at the earliest phase of functional differentiation after priming, termed "early effector cells" (EEC), which also exhibited an activated non-exhausted phenotype, but was less differentiated and associated with coexpression of multiple inhibitory receptors. In response to autologous tumor, EEC upregulated CD107a, produced IL-2 and IFN-gamma and were competent for differentiation. The identification of EECs marked by inhibitory receptor expression at tumor sites will enable investigations of early stages of adaptive anti-tumor immunity, as well as support the rationale for administering immunotherapy in early stage NSCLC.