Behagen was born in Hamburg, the son of wine merchant Anthony Behagen and Petronelle Elisabeth Mestecker. His father died when he was two years old. His mother later moved to Copenhagen where she married the wealthy merchant Joost van Hemert in 1732. Behagen joined his step father's company. He married Elisabeth Gertrud Wasserfall on 9 April 1755 in the Reformed Church in Copenhagen.
In 1776, he became etatsråd and in 1782 he was ennobled with a right to use a coat of armsdating from his ancestors. He died on 17 December 1783 and is buried in the graveyard of the Reformed Church in Copenhagen.