Marcel Vandewattyne was most successful as a cross country runner. Starting after World War II, during which Vandewattyne was a member of the resistance, he competed a record 20 times in the International Cross Country Championships, the forerunner of the IAAF World Championships. He won the silver medal three times, in 1946, 1952 and 1962. But Vandewattyne was also an excellent track runner, competing in two Olympics (1948, 1952) and two European Championships, where he placed 7th in the 10,000 m (1950) and eighth in the 3,000 m steeplechase (1946). He won 11 Belgian titles, six in cross country, three in the 10,000 m and two in the steeplechase. After his running career, he remained active for his club ASSA Ronse, among others serving as the club's vice-president.
Personal Bests: 5000 – 14:18.2 (1958); 10000 – 30:06.4 (1962).