Ovarian cancer, ranking fifth in cancer mortality, presents a significant therapeutic challenge. The immunomodulatory functions of CD38in epithelial ovarian cancer (EOC) and its influence on the tumor microenvironment (TME) remain poorly understood. Public datasets, RT-qPCR and immunohistochemistry (IHC) were used to analyze CD38 expression and clinicopathological features in EOC. Gene manipulation techniques were employed to elucidate its functions, while integrated IHC and bioinformatics were conducted to assess its involvement in immune/stromal infiltration. Immune-related functions of CD38 were explored using GO, KEGG analysis and TIP database. TIDE algorithm was employed to predict the correlation between CD38 and immune checkpoint blocking responsiveness. CD38 inhibitor efficacy was evaluated in an EOC mouse model, with flow cytometry monitoring cellular changes. The involvement of CD38 in the PI3K-AKT and IL-6 signaling pathways was evaluated using RT-qPCR, western blot, and publicly datasets. CD38 is significantly upregulated in EOC, influencing the cell proliferation and metastasis. It regulates the PI3K-AKT and IL-6 signaling pathways, thereby increasing tumor malignancy. CD38 is also upregulated in immune and stromal cells, affecting TME remodeling by facilitating immune cell and CAF infiltration, impeding T cell recognition of tumor cells, and enhancing CAF-tumor cell communication. Additionally, CD38 correlates with multiple immune checkpoint molecules. Notably, CD38 inhibitor therapy inhibited effectively EOC progression and modulates immune responses. Elevated CD38 expression is associated with EOC progression, TME remodeling, and immune response modulation. Thus, CD38 could be a promising target for ovarian cancer immunotherapy.