Pancreatic cancer (PC) patients have poor prognosis and survival rate. Gemcitabine, the drug of choice has a dismal 15% response rate. Earlier, we reported that Garcinol alone and in combination with gemcitabine showed a dose-dependent favorable response on PC cell lines. This study probes the in vivo effects of dietary Garcinol on PC progression in transgenic PC mice (KPC; K-ras and p53 conditional mutant). KPC male mice were divided into: KC- Control diet; KGr-0.05% Garcinol diet; KGm-Gemcitabine injected; KGG - Garcinol diet + Gemcitabine injected groups. Changes in tumor progression, toxicity, or cell morphology were monitored by magnetic resonance imaging, Fore-stomach, and blood smear, respectively. Pancreatic Intraepithelial Neoplasia (mPanIN) grading with hematoxylin and eosin (HE) staining was conducted on pancreas and validated by immunohistochemistry. The KGr group showed improved survival, no observable toxicity with marked reduction in papilloma formation in the fore-stomach, and a higher ratio of NK and NKT cells compared to Non-NK lymphocytes. Additionally, the KGr, KGm, and KGG groups showed reduction in tumor volumes and reduced number of advanced mouse PanIN3. Dietary Garcinol alone and in combination with gemcitabine retarded the progression of PC in transgenic PC mice, arresting the cancer in the earlier stages, improving prognosis and survival.