Prostate cancer (PCa) is the most frequent visceral neoplasm and the third leading cause of cancer-related deaths in men worldwide. While current treatments are effective for localized disease, those for metastatic forms, occurring de novo or following therapeutic resistance, have poor outcomes. Indeed, docetaxel, the main chemotherapeutic agent, improves the survival by only a few months. Therefore, it is of utmost importance to identify new biomarkers and therapeutic strategies. Epidemiological studies have correlated vitamin D deficiency with PCa severity. In line with these results, we showed that vitamin D levels in a French cohort are negatively associated with those of prostate-specific antigen (PSA), the current clinical biomarker for PCa progression. However, the role of vitamin D receptor (VDR) in tumor progression remains unclear, and its targeting in clinical trial provides contrasting results. The tumor suppressor PTEN is frequently mutated in human PCa and associated with metastasis and treatment resistance. We showed that Pten(i)pe−/− mice, in which Pten is selectively inactivated in prostatic epithelial cells (PEC) at adulthood, recapitulate the human disease. In addition, we demonstrated that VDR inactivation in Pten(i)pe−/− mice promotes oxidative stress, increases PEC proliferation, and enhances immunosuppressive neutrophil infiltration. Notably, tumor dissemination to the liver, associated with poor prognosis in patients, is enhanced in mice with Pten and Vdr inactivation. Importantly, we identified circulating neutrophils as a promising biomarker and therapeutic target to prevent tumor spread. Given the protective role of VDR, and hypercalcemia being a major limitation for the use of bioactive vitamin D (1,25D3) clinically, we explored analogs with enhanced anti-proliferative properties and reduced calcemic effects as promising therapeutic options. Treatments of Pten(i)pe−/− mice at an advanced tumor stage with a low-calcemic vitamin D analog induced apoptosis and reduced neutrophil infiltration. Single-cell RNA sequencing further revealed that while a subset of PECs is eliminated, others resisted through activation of anti-apoptotic pathways, highlighting mechanisms that may explain the contrasting results observed in the clinic. In line with these results, we showed that in monotherapy, VDR ligands had no effects on chemoresistant PCa cells isolated from a patient’ adenocarcinoma. However, we demonstrated that in combination with docetaxel, vitamin D analogs overcome chemoresistance in these cells, as well as in a patient-derived xenograft. Together, these studies provide critical highlights into the role of vitamin D signaling in PCa progression and propose new biomarkers and therapeutic strategies, opening new avenues for the clinical care of advanced and chemoresistant PCa.