Generation of memory CD8 +T cells is necessary for the establishment of protective T cell immunity against pathogens. The understanding of the cellular and molecular processes involved in the formation of memory CD8 + T cells remains elusive. Current knowledge gaps may stem from reliance on specific pathogen-free (SPF) models, where restricted microbial exposure creates an immunological milieu that diverges from natural environments. Here, we demonstrate that under non-SPF housing, CD1d +/− and Ja18 +/− mice show enhanced central memory (TCM) formation versus CD1d-restricted NKT-deficient (CD1d −/−/Ja18 −/−) controls, implicating CD1d-restricted NKT cells in TCM formation. Mechanistically, CD1d-restricted NKT cells elevated CD4 + T cell-derived IL-15 in CD1d +/- mice, activating the IL-15/pSTAT5/Eomes axis essential for TCM maintenance. Functional validation through CFSE-labeled OT-1 memory cell transfers revealed an NKT-dependent survival advantage in CD1d +/− hosts, providing direct evidence for microbial-experienced niches in shaping immune memory. These findings establish CD1d-restriced NKT cells as physiological regulators of TCM generation, suggesting their potential utility as vaccine adjuvants to enhance protective immunity.