Jensen won the inaugural 1975 edition of Amsterdam Marathon on 3 May 1975, clocking 2:16:51. He ran the Olympic marathons in 1972 and 1976 and finished in 30th and 28th place, respectively.
Between 1966 and 1976 Jensen won eight national team titles (4 × 1500 m relay and cross-country) and eight individual titles, in the 5000 m (1966), 10000 m (1973), 20 km (1972 and 1974) and marathon (1973-1976).
