In biliary-pancreatic malignancy, the serum CA 19-9 is considered as a tumor marker. Its high level may indicate the presence of a malignant disorder, but it can also be raised in benign conditions and also in malignancies from other organs. The value may be normal even in malignant condition. This comparative study was conducted in the Department of Surgery of Bangabandhu Sheikh Mujib Medical University (BSMMU), Bangladesh from 1st June 2016 to 31st May 2017 to determine the sensitivity and specificity of CA 19-9 as a tumor marker in pancreatic malignancy in our perspective and to establish a cut-off value of CA 19-9 which might prove as a definitive indication of pancreatic malignancy. We found that when the cut off value of CA 19-9 is 38 U/ml (according to ROC curve), the sensitivity, specificity, PPV and NPV were 77.8%, 77.8%, 77.8%, 77.8% respectively. And if the serum CA 19-9 threshold was raised to 100 and 120 to diagnose pancreatic cancer, sensitivity became 72.2% and 66.7% and NPV 76.2% and 73.9% respectively. However, the specificity increased to 88.9% and 94.4% and the PPV increased to 86.7% and 92.3% respectively.