Kohn played as a striker, and spent most of his career plying his trade abroad, in Germany, Switzerland, and finally Netherlands, where he later became a successful manager. During his playing days, he earned the nickname "Spitz" for his ferocity and goal-scoring instinct.
Kohn made his debut for Luxembourg in a September 1953 World Cup qualification match against France, in which he immediately scored a goal. He went on to earn 7 caps, scoring one goal, all of them in FIFA World Cup qualification matches. He won a total of 16 caps (6 goals) including unofficial matches.
He played his final international game in September 1965, a 2–5 defeat by Yugoslavia.
After retiring as a player, Kohn became manager at FC Twente in 1972 and clinched runner-up spot in the Eredivisie in the 1973/1974 season. In May 1975 they reached the UEFA Cup Final, losing 1–5 on aggregate to German side Borussia Mönchengladbach.
He moved on to Go Ahead Eagles and Club Brugge before rejoining Twente in the 1982/1983 season, but he could not save them from relegation that year. After 5 rounds in the 1988/1989 season Kohn became the responsible manager at Ajax, his assistant being Louis van Gaal.