Several skeletons, potshards, weapons, and jewels were discovered here, dating from the 5th and 6th century, attesting to Seraing being inhabited in Frankish times. The first mention of Saran dates from 956, when a Carolingian farming domain extending on both sides of the Meuse River and owned by someone named Saran was donated to the abbey of Sint-Truiden. The whole territory soon passed to the Bishopric of Liège. In the 11th century, Prince-Bishop Henri I of Verdun used a house in Seranus to entertain guests. Throughout the Middle Ages, the inhabitants of Seraing owed allegiance to Liège, pledging to defend the fluvial approach to the city in case of invasion, in exchange for tax exonerations. The first wooden bridge across the river, which replaced the ferry, was built in 1381.
The name of the town changed several times throughout its history, with the current spelling only being set in the 18th century. At around that time, various factors combined to attract industrial investors to Seraing: the advent of the Industrial Revolution, the proximity of the Meuse River, and the discovery of coal at Ougrée. The first ironworks were founded there in 1809. John Cockerill revolutionized the steel industry by using blast furnaces and coke instead of traditional charcoal. These inventions would be the basis for his new company, John Cockerill & Cie established in Seraing in 1817. Over the next decades, many more metallurgical plants and foundries were built in this area, which became an integral part of Wallonia's industrial backbone, the sillon industriel. Glassworkers found the proximity of a cheap source of coal attractive. The Val Saint Lambert started its operations in 1826.
The Val Saint Lambert site includes the old Val-Saint-Lambert Abbey and the crystal manufacture, where glass workers still blow, carve, and etch the world-famous pieces of art. The neighbouring castle houses a glass museum.
The Cockerill castle used to be the summer residence of the prince-bishops of Liège, then a hospital under Napoleon, a powder magazine, and the personal property of William I of the Netherlands, who ceded it to the Cockerill family in 1817.
Besides the Cockerill castle, the historic centre of the city also includes the city hall and the main church, which harbours 12th-century baptismal fonts.
The forested region south of Seraing offers a multitude of strolls and hikes.
According to an old local legend, witches (Walloon: macrales) abound in the Seraing area. The macrales have been resurrected in the year 2000 and are now a regular staple of the local folklore.
Like many other towns in Wallonia, Seraing has its own giant puppet: Li Rayeû d’class.
Seraing also counts a number of colourful associations, including a coopers’brotherhood, whose goal is to revive the wineries of the Val Saint Lambert abbey, and the “Gay Boulet” brotherhood, whose mission is to popularize the “Boulet Liégeois”, a local recipe.