Gerschau was born 1963 in the West German city of Bremen and grew up in Bremerhaven and, following his move to Wilhelmshaven, later earned his Abitur in Bremen. After completing his military service in Bremen and Schleswig-Holstein, Gerschau moved to Hanover.[4]
In 1984 Knut Gerschau and Robert Kroth founded the Gerschau.Kroth.Werbeagentur. GmbH (now LEADS-Marketing) in Hanover. He has been their managing partner since the company was founded.[4]