In different eras, Iran has always been the center of various sciences especially pharmacy and herbalism. Origin of Iranian medical sciences backs to Avestan period and by emergence of Zoroaster, who was a noble physician. Extense of this knowledge along with others had been expanded which, in turn, had influenced other nations. However, despite impressionability of other nations from Iranian sciences, unfortunately no ancient source for the history of medicine in Iran remained, and all documents regarding these issues had been destroyed due to fire arisen from invasions and wars which burnt down Iranian cultural databases and historical documents. From among these issues, we can mention Iranian traditional medicine which merely exists in Avestan and some Pahlavi books and there are a few point-outs in Greek documents, and unfortunately, there have not yet been any documents and sources in Iranian medicine. Hence, Iranian medical history is divided into three distinct periods: The first period, from pre-Avestian and Avestian eras to emergence of Sassanid Empire; second from beginning to extinction of Sassanid dynasty, and the third, from emergence of Islam up to now, which is known as the golden ages of Iranian sciences. This article is a brief research on the first period of Iranian medicine which begins with Avestian citation to Fereydun (the first physician,) and will continue up to the beginning of Sassanid Empire.