Despite the clinical approval of CAR-T cell therapies for hematological malignancies, their success in solid tumors remains limited due to several factors including antigen escape, immunosuppressive tumor microenvironment (TME), and poor T-cell trafficking to the tumor site. NKG2D CAR-T cells, recognizing multiple stress-inducible NKG2D ligands (NKG2DLs), offer a promising but modest antitumor benefit. Pharmacological agents capable of enhancing NKG2DLs expression and remodeling the TME may overcome these barriers. Here, we identified dihydroartemisinin (DHA), a clinically approved antimalarial compound as a novel inducer of NKG2DLs in tumor cells at non-cytotoxic concentrations without affecting primary human T cells. Transcriptomic analysis revealed that this effect involves activation of DNA damage response, p53, and PI3K/Akt signaling pathways. In addition, DHA upregulated MHC-I and suppressed B7-H3 expression, promoted secretion of T-cell–recruiting chemokines (CXCL9, CXCL10), and polarized macrophages toward an M1-like phenotype, thus contributes to an immunostimulatory TME. Functionally, DHA pretreatment of tumor cells significantly enhanced NKG2D CAR-T cell activation, trafficking, and cytotoxicity. In pancreatic and prostate xenograft models, DHA combined with NKG2D CAR-T cells increased intratumoral T-cell infiltration which led to significant tumor control without any systemic toxicity. This study provides the first evidence that DHA upregulates tumor NKG2DLs and reprograms the TME through modulation of tumor immune axis. Our findings establish DHA as a clinically accessible pharmacological adjuvant with strong translational potential to improve NKG2D CAR-T therapy against solid tumors.