At the 1958 European Athletics Championships, held in Stockholm, Dahl set a Swedish record and championship record at , beating Jiří Lanský and Stig Pettersson. He became the fourth, and thus the latest male Swede to win the title, following Kurt Lundqvist, Anton Bolinder and Bengt Nilsson. For this performance he was awarded the Svenska Dagbladet Gold Medal and designated the Stora grabbars märke number 200 in athletics.