To the best of our knowledge, this is the first study to (i) demonstrate that plasma miR-33a levels could be a valuable biomarker and an important prognostic factor for human pancreatic cancer; (ii) provide evidence that miR-33a synergistically increases the sensitivity of PDAC cells to gemcitabine; (iii) identify Pim-3 as a direct binding target of miR-33a; and (iv) demonstrate that miR-33a downregulates Pim-3 to inhibit tumor growth and chemoresistance, in part via the AKT/Gsk-3β/β-catenin signaling cascade, in pancreatic cancer. Here, GSK3B is linked to familial pancreatic carcinoma.