Mucoadhesive drug delivery systems interact with the mucus layer covering the mucosal epithelial surface, and mucin molecules increase the residence time of the dosage form at the site of absorption. Bioadhesion may be defined as the state in which two materials, at least one of which is of a biological nature, are held together for extend periods of time by interfacial forces Mucosal layer represents potential sites for the attachment of any bioadhesive systems because mucosal layer lines number of the body including the gastro intestinal tract, the urogenital tract, vaginal tract, the eye, ear, and nose. The mucoadhesive Bilayer tablets consisting of two various types of drug molecules and they show on set of actions at their particular sites. This review describes the structure of mucosal layer, mechanism of action of mucoadhesion, and preparation techniques of Bilayer tablets and evaluation parameters of tablets.