In Braunau am Inn, Eberhartinger grew up and graduated in 1968. He then stayed for a year in the United States of America, before he began medical studies in Graz. It was in Graz, where he met the sister of Thomas Spitzer, who had founded Erste Allgemeine Verunsicherung. Finally Eberhartinger interrupted his studies, took on various jobs in Munich, and finally bought a Land Rover to travel throughout Africa. He returned to Austria and resumed his studies in Graz, until in 1981 when he joined Thomas Spitzer's band Erste Allgemeine Verunsicherung and went on helping it to become the band they are best known for today.
In 1985, Klaus Eberhartinger's son Christopher was born, who went on to study in Barcelona at the Business School. Klaus Eberhartinger is still close to his mother and she takes care of his financial affairs. Since the mid-90s Eberhartinger usually spends half the year in Kenya, where Thomas Spitzer has bought a house.
In addition to several CD releases and tours of Erste Allgemeine Verunsicherung, Eberhartinger occasionally played the role of Gailtalerin in the stage play "Der Watzmann Ruft" ("The Watzmann calls") This successful production was on tour for two years.
In the third season of the Austrian version of "Dancing with the Stars" in the spring of 2007 he won first place with his dance partner Kelly Kainz, despite the fact he had broken a rib during training. Shortly after, he took over hosting the ATV show "Quiz Champion". On the 10 March 2008, he published his first book entitled "Sex, Lachs & Rock'n'Roll" (Sex, Salmon and Rock 'n'Roll).