This chapter discusses the Brazilian-Italian cooperation in the nuclear field between the early 1950s and 1986. Since the late 1930s, Italian or Italian-Brazilian scientists promoted the development of studies in nuclear physics. Immediately after World War II, the Brazilian-Italian collaboration continued. Between the 1950s and the 1970s, Brazilian nuclear scientists studied in Italian institutions. Relying on primary sources from Brazilian archives and oral history interviews with protagonists of the Brazilian nuclear program, this chapter explore the relations between Italy and Brazil from 1951, the year of the establishment of the Brazilian nuclear program, until the 1980s. This study focuses on the bidirectional transfer of knowledge on sensitive technologies, and on the formal and informal cooperation between the two countries.