Ahlefeldt was born at Hardenburg as the youngest son of Grand Chancellor Count Friedrich von Ahlefeldt-Rixingen and his second wife, Countess Marie Elisabeth of Leiningen-Dagsburg-Hartenburg (1648-1724).

In 1696, he replaced Johan Georg Holstein as the Hofmeister of Prince Carl on a four-year journey to Germany, Switzerland, France, Italy and the Netherlands.

Together with Christian Gyldenløve, he belonged to the inner circle around the young king Frederick VIV, which overshadowed both Grand Chancellor Conrad Reventlow and gehejmeråd Chr.

As a member of konseillet, together with Otte Krabbe and Christian Sehested Ahelfeldt was responsible for the government in Copenhagen during the plague outbreak in 1711, while the king sought refuge at Koldinghus.

He therefore also inherited the county of Langeland (including Tranekær) and the estates Søgård, Gråsten, Ballegård, Grøngrøft and Årup im Slesvig and Die Wildniss at Glückstadt.

In 1702, Carl von Ahlefeldt acquired an estate at Kongens Lyngby north of Copenhagen, where he commissioned the architect François Dieussart to build the first Sorgenfri.