For many decades for the treatment of disease many of the dosage form are using which are including tablets, capsules, pills, creams, ointments, liquids, injectables. To maintain the concentration of drug it is necessary to take these types of dosage form several times of day. A novel drug delivery system thus aim at releasing one or more drug continuously at a predetermined pattern for a fixed period of time, either systematically or to a specific target organ. Transdermal drug delivery system includes all topically administered drug formulations intended to deliver the active ingredients into the circulation. A patch contained high dose of drug which is retained on the skin for prolonged period of time. Drug from patch enters into blood flow via diffusion process. Skin contains 10-70 hair follicles and 200-250 sweat ducts per cm2 of the skin so it is easily accessible by drugs. Drug can penetrate through skin via three pathways- through hair follicles, sebaceous gland, and sweat ducts. Its main advantages includes controlled drug release with minimum side effects, improved bioavailability, bypass first pass metabolism and many more. There are factors such as physiochemical as well as biological which affect the bioavailability of transdermal medicament. Due to technological advancement, many new techniques which have attained attention are Iontophoresis, phonophoresis, Electroporation and micro needles etc. This review covers general aspects regarding transdermal patches like advantages, basic components of transdermal drug delivery system, methods of preparation of transdermal patches and evaluation