While cancer immunotherapy has primarily focused on CD8 T cells, CD4 T cells are increasingly recognized for their role in antitumor immunity. The HLA-DRB3*02:02 allele is found in 50% of Caucasians. In this study, we screened HLA-DRB3*02:02 patients with melanoma for tumor-specific CD4 T cells and identified robust New York esophageal squamous cell carcinoma 1 (NY-ESO-1)123-137/HLA-DRB3*02:02 CD4 T cell activity in both peripheral blood and tumor tissue. By analyzing NY-ESO-1123-137/HLA-DRB3*02:02-restricted CD4 T cell clones, we uncovered an unexpectedly high cytotoxicity, strong T helper 1 polarization, and recurrent αβ T cell receptor (TCRαβ) usage across patients and anatomical sites. These responses were also present in other NY-ESO-1-expressing cancers. TCRs from these clones, when transduced into primary CD4 T cells, showed direct antitumor efficacy both in vitro and in vivo. Our findings suggest that these TCRs are promising for adoptive T cell transfer therapy, enabling broader targeting of NY-ESO-1-expressing adult and pediatric cancers in clinical settings.