In 860, King Louis the German of East Francia donated the lands of the estate ad Friesah - derived from Slavic Breza (birch) - in the Bavarian March of Carinthia (Carantania) to Archbishop Adalwin of Salzburg.

About 1076 Archbishop Gebhard of Salzburg, a follower of Pope Gregory VII in the Investiture Controversy, had the Petersberg fortress erected above the town in order to prevent Emperor Henry IV from crossing the Alps.

During the Middle Ages, it was a principal market town and commercial centre due to an important trade route from Vienna to Venice that ran through the city.

From local silver resources it even minted its own currency called the Friesacher Pfennig or Frizatik, widely used within the Austrian and Hungarian lands in the 12th century.

The fortress, however, continued to be an important power basis of the Salzburg prince-archbishops throughout the Middle Ages, once again enlarged and strengthened by Leonhard von Keutschach from 1495 onwards.

In 2021, the town began fulfilling much of the electricity and hot water demands by way of the largest solar farm in Austria, a nearby 5,750 square metre installation that generates 2.8 million kilowatt-hours of power per year.