Thermoelectric coolers, also called thermoelectric modules or peltier coolers, are semiconductor-based electronic components that function as small heat pumps. On applying a low DC voltage to the thermoelectric module, heat moves through the module from one side to the other. One face of the module is therefore cooled, while the other face simultaneously heats up. This phenomenon may be reversed whereby a change in the polarity of the applied DC voltage will cause heat to be moved in the opposite direction. consequently, a thermoelectric module may be used for both heating and cooling, which makes it highly suitable for precise temperature control applications. Conventional coolers used in homes and industries rely on refigerants such as hydro fluoro carbon, which is a threat to the ozone layer of the earth. On the other hand , thermoeletric coolers are environment friendly, compact and affordable. This paper describes the operating principles, constructional details, applications, advantages and disadvantages of thermoelectric coolers. Thermoelectric coolers are semiconductor based devices. They have got several advantages like solid construction, quiet & reliable operation, no CFC?s, precise temperature control. A thermoelectric cooler permits lowering the temperature of an object below ambient as well as stabilizing the temperature of objects above ambient temperatures. Thermoelectric coolers can be used for applications that require heat removal ranging from milli-watts up to several thousand watts. Therefore they are used for the most demanding industries such as medical, laboratory, aerospace, semiconductor, telecom, industrial, and consumer. Uses range from simple food and beverage coolers for an afternoon picnic to extremely sophisticated temperature control systems in missiles and space vehicles. A thermoelectric cooler provide a solution that is smaller, weighs less, and is more reliable than a comparatively small compressor system. It offers a convenient earth friendly alternative. Researchers are working on improving the efficiency of thermoelectric devices , reducing their cost and increasing their applications.