The transdermal drug delivery system is one of the novel drug delivery system which overcome the problems arises from conventional dosage forms. Transdermal drug delivery has a major role in increasing patient compliance and avoiding first pass metabolism. It is one of the alternative method for oral route of drug administration. This review gives valuable information about the TDDS like its advantages, disadvantages, types of TDDS, different methods for formulation, and different methods of evaluation of transdermal patches.