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T cell exhaustion limits anti-tumor immunity and responses to immunotherapy. Here, we explored the microenvironmental signals regulating T cell exhaustion using a model of chronic lymphocytic leukemia (CLL). Single-cell analyses identified a subset of PD-1hi, functionally impaired CD8+ T cells that accumulated in secondary lymphoid organs during disease progression and a functionally competent PD-1int subset. Frequencies of PD-1int TCF-1+ CD8+ T cells decreased upon Il10rb or Stat3 deletion, leading to accumulation of PD-1hi cells and accelerated tumor progression. Mechanistically, inhibition of IL-10R signaling altered chromatin accessibility and disrupted cooperativity between the transcription factors NFAT and AP-1, promoting a distinct NFAT-associated program. Low IL10 expression or loss of IL-10R-STAT3 signaling correlated with increased frequencies of exhausted CD8+ T cells and poor survival in CLL and in breast cancer patients. Thus, balance between PD-1hi, exhausted CD8+ T cells and functional PD-1int TCF-1+ CD8+ T cells is regulated by cell-intrinsic IL-10R signaling, with implications for immunotherapy. [Display omitted] • Heterogeneous PD-1 expression identifies CD8+ T cells with distinct functions in CLL • IL-10 prevents activation-induced exhaustion of CD8+ T cells and reduces CLL development • By altering chromatin in CD8+ T cells, IL-10R blockade disrupts NFAT:AP-1 cooperativity • IL-10R loss correlates with T cell exhaustion and poor survival of cancer patients T cell exhaustion limits anti-tumor immunity and responses to immunotherapy. Using a model of chronic lymphocytic leukemia, Hanna, Llaó-Cid, et al. reveal that the balance between PD-1hi, exhausted CD8+ T cells and functional PD-1int CD8+ T cells that are associated with tumor progression or tumor control, respectively, is regulated by cell-intrinsic IL-10R signaling. [ABSTRACT FROM AUTHOR]