In 1961, Harald Nielsen moved abroad to play professionally for Bologna F.C. in Italy. At Bologna, "il freddo danese" (the cold Dane) was a part of the 1963–64 Serie A winning squad, and he was the Italian league topscorer in both 1963 and 1964. Following six seasons at Bologna, Harald Nielsen moved to Inter in 1967, in a transfer deal which made him the most expensive player in the world at the time. Although he started by winning the unofficial world cup for teams by beating Santos with Pelé 1–0 in New York, Nielsen did not find the same degree of success with Inter as in Bologna, and following years at S.S.C. Napoli and U.C. Sampdoria a back injury kept him mostly off the field, he ended his career in 1970.