Tumors that contain tumor-infiltrating lymphocytes (TIL) with tissue-resident memory T cells (TRM) features are associated with better patient prognoses. While CD8+ T cells that target tumors often fail to restrain tumor growth due to progressive T cell exhaustion, pathogen-specific TRM survey tissues and sustain protective capacity for years. We identified protein homeostasis (proteostasis)-related E3 ubiquitin ligase genes shared by TRM and progenitor-exhausted TIL (TPEX), that are lost as TIL become terminally-exhausted (TEX). Sustained ligase expression led to increased TCF1+ T cell accumulation and improved anti-tumor function and less T cell exhaustion in chronic infection. Loss-of-function in cancer models impaired TIL accumulation and function and altered T cell differentiation in response to acute infection. Low-input mass spectrometry revealed abundant expression of protein degradation pathways by TEX, yet they accumulated unfolded proteins. Ligase overexpression rescued unfolded protein accumulation in TEX, demonstrating their functional contribution to proteostasis. Ligase overexpression in combination with immune checkpoint blockade led to improved survival from murine melanoma, demonstrating that the relationship between proteostasis and T cell differentiation opens up new avenues for cancer immunotherapy.