Disclosed are a bilayered composite tablet formation comprising (a) a first layer comprising irbesartan or a pharmaceutically acceptable salt thereof; and (b) a second layer comprising atorvastatin or a pharmaceutically acceptable salt thereof and magnesium carbonate (MgCO3) in a weight ratio of 1:4 to 1:5, and a method for preparing the same. Exhibiting excellent dissolution rates and bioavailability, the bilayered composite tablet formulation is useful as a therapeutic for hypertension and hypercholesterolemia.