Benny Kohlberg had his breakthrough at the 1978 Swedish Ski Games. He competed in his first Winter Olympics at Lake Placid in 1980 in three events, with his best result being a fifth place with the Swedish relay team. Four years later in Sarajevo, he had his greatest achievement with a gold medal in the relay together with his teammates Thomas Wassberg, Jan Ottosson and Gunde Svan, with Kohlberg running the second leg. His best individual finish at a World Cup competition was a third place in 1982 in Switzerland. His only Swedish Championship came in 1982 when he won the 30 km. Back problems and a herniated disk posed long-term problems for Kohlberg. After his active career he worked as a serviceman in the ski industry for some time, but later worked in a sawmill in Lässerud close to his home in Arvika.