It was raised to archiepiscopal status during the reign of Charlemagne, whose will mentions the bishoprics of Metz, Toul and Verdun as its suffragans.

In 816 Louis the Pious confirmed to Archbishop Hetto the privileges of protection and immunity granted by his father.

In 898, Archbishop Radbod received complete immunity from all taxes for the entire episcopal territory, granted by Zwentibold, who was the natural son of Emperor Arnulf of Carinthia, and who reigned briefly as King of Lotharingia.

Following Zwentibold's assassination in 900, the handlers of the child-king Louis courted Radbod in their turn, granting him the district and city of Trier outright, permission to impose customs duties and the right to a mint (as much a symbol of independent authority as an economic tool).

From the court of Charles the Simple, he obtained the final right of election of the Bishop of Trier by the chapter, free of Imperial interference.

In 1473, Emperor Frederick III and Charles the Bold, Duke of Burgundy held a meeting in Trier.

During the Thirty Years' War, Archbishop-Elector Philipp Christoph von Sötern supported France against the Habsburgs, leading to a rivalry between French and Spanish troops about the strategic cities and fortresses of the Electorate.

In 1630, the city of Trier opened its gates to Spanish troops to defend its rights against the absolutist Elector.

After a short period of peace, the War of the Polish Succession started in 1734; the following year Trier was again occupied by the French, who stayed until 1737.

From 1795, the territories of the Electorate on the left bank of the Rhine were under French occupation; in 1801, they were annexed and a separate French-controlled diocese established under Bishop Charles Mannay.