Bertelsen was born in Haderslev. During his club career, he played for Danish clubs Haderslev FK, Esbjerg fB and OB, and Scottish sides Greenock Morton, Dundee and Kilmarnock. He played 20 times for Denmark between 1962 and 1964, scoring nine goals. He played for his country at the 1964 European Nations' Cup, placing fourth at the end of the tournament.