The Iron Age ended around 300 BC and a different era, influenced by the Seleucid culture of both Mesopotamia and Syria, started in the region. Unlike the former culture of the so-called Iron Age the site of Mleiha belongs to a new culture and is considered the largest known settlement representing this period in the region. Domestic buildings and monumental graves, perhaps originally similar to those of Al Fao in Saudi Arabia and Petra in Jordan, were discovered. Apart from the production of iron, which was widely used in this period, we see coin minting and writing at Mleiha for the first time. The one-sided coin mould found at the site bears the head of Hercules. Coins, also bearing such a head, as well as a figure sitting on a stool - probably a god or, a ruler - on the other side, were known at the site. Inscriptions in the Aramaic language, as well as some texts of South Arabian inscriptions, were also discovered.

The other site representing the second phase of this culture is ad Dour. This site which must have been already a large harbour during the first century AD reached its climax during that time. Most of its architectural remains and the discovered objects go back to the above-mentioned period. Before the termination of ad-Dour and the last phase at Mleiha, the Parthian influence remained visible for a short time. This influence dwindled during the following period when a new era started. The influence of the Sasanian Empire became very much apparent during this period.