Since the previous four decades, the idea of mucoadhesion has attracted a great deal of attention in the many pharmaceutics sectors. The mucoadhesive drug delivery system has many benefits that make it an innovative method for the local and systemic administration of various medications. This medication delivery system's primary benefit is that it extends the dosage form's stay in residence at the application site. The phenomenon of interfacial molecular attractive forces between a biological membrane's middle layer and natural or synthetic polymers, which enables the polymer to cling to that membrane's surface for an extended as well as protracted period of time, is known as bioadhesion. Mucoadhesive drug delivery systems are available in the form of tablets, films, patches, and gels for oral, buccal, nasal, ocular, vaginal, rectal and topical routes for both systemic and local effects. To design an effective particulate drug delivery system having mucoadhesive function, several mucoadhesion tests for polymers and for the resultant delivery systems should be developed. This paper lays main emphasis on the mechanism of bioadhesion, various bioadhesion theories, various types of mucoadhesive dosage forms, various types of mucoadhesive polymers, and various evaluation methods.