The son of a famous German speedway champion, Kurt Ahrens was always known as Kurt Ahrens Jr. during his early racing career which began in 1958 in Formula 3 events. It was not until 1961 that he rose to prominence by winning the German Formula Junior title. He repeated the success in 1963 after the 1962 season was spoiled by a ban. His father retired from the sport in 1963 and two years later Kurt Jr acquired a Brabham Formula 2 car and began to make a mark at international level. He also took part in touring car events at the wheel of a factory Fiat and in the course of the next few years he raced mainly in F2, taking part in three German GPs in the F2 class. In 1968 he drove a Caltex-sponsored third works Brabham at the German event.
In 1969 he joined the Porsche factory sportscar team and shared victory with Jo Siffert in the Austrian 1000 event. The following year he partnered Vic Elford to victory in the Nurburgring 1000. He retired in 1971 and concentrated on building up the family's car dealership and a scrap metal business.