Iasos was built by Argonauts from the city of Argos in the 9th century BC but it later came under the dominance of Miletus. In the 5th century BC it came under the control of Athens and from the 4th century BC, it was managed by Mausolos, the king of Halicarnassus.

During Roman times it became the tax center for all the province of Asia Minor. Iassos is known to have been a very rich city. One of its principal exports was salted fish. The fish bazaar was very important for the city and when the bell of the bazaar was rung people used even to leave the theatres and run to the harbor.