It is said that the origin of the city was a resting point for travellers. There was a cafe with a woman named Seiyun there, and the area was named after her in her honor. Since then, the city has become the largest area of Hadhramaut valley.
It is served by Seiyun Airport. It is also well known for the Seiyun Palace of the Sultan of Kathiri built in s by mud and stones. It is overseeing the market place for merchants coming from outside. Seiyun is first mentioned in the beginning of the 4th-century, which dates back to the reign of King Dhamar who ruled at the beginning of the 4th-century the area around Hadhramaut Valley and known for destroying sixty thousand columns in the area.
Destruction of the columns confirms that the Hadhramaut region was undergoing an economic prosperity owing from spread of grape cultivation in large areas under the climatic conditions different from the current circumstances.
Seiyun during the Islamic period emerged as a village in the era of the Rashidun Caliphate. It was administratively followed by the city of Tarim. This was the case during the Umayyad period as well. In , it became administratively affiliated with the city of Shibam, however the son of Haritha had led the revolution in But it gained its autonomy only in the year when it became the capital of the valley in the era of Badr Abu Tuwairq , where an administrative unit consisted of a sultanate that extended from Ain Ba to the west of the city of Dhofar was founded.
In the 18th-century, Yafa conquered the cities of Hadhramaut and took over many parts of Seiyun, where the state was established. Its fortified fortress, the Sultan's Palace, was the seat of Sultan al-Kathiri. Postage stamps from the Sultanate were sometimes inscribed "Kathiri State of Seiyun.
