Only the east of the Saar Territory, today's Saar-Palatinate district, formerly the western fringes of the then Bavarian Rhenish Palatinate, was previously no part of the Trier Region.

Koblenz Region's former areas make up part of today's St. Wendel district in the Saarland.

In December 1946, when a new customs boundary dissected the Saar Protectorate (later becoming the Saarland) from the area under the Allied Control Council over Allied-occupied Germany, the Trier Region with its then remaining territory had become one of the then five regions forming the new state of Rhineland-Palatinate, founded in August 1946.

Later, the French occupation government again redeployed some municipalities – some returned to Allied-occupied Germany, some newly annexed to the protectorate – between the Saar area and the new state of Rhineland-Palatinate in 1947 and 1949, before the border was finally fixed.

Since 2000, the employees and assets of the Bezirksregierungen (i.e. regional administrations) form the Aufsichts- und Dienstleistungsdirektion Trier (ADD; Supervisory and Service Directorate Trier) and the Struktur- und Genehmigungsdirektionen (SGD; Structural and Approval Directorates) Nord in Koblenz and Süd in Neustadt (Weinstraße).