He served as the Italian ambassador to Canada from May 1990 to January 1994. He then became the Deputy Secretary General of NATO before briefly becoming acting Secretary General twice. Firstly by replacing Manfred Wörner on August 13, 1994 after the latter resigned in the last stages of cancer. He was then replaced by Willy Claes on October 17, 1994 who resigned on alleged corruption charges on October 20, 1995.
Balanzino, who had gone back to being Deputy, again took over the reins until he was replaced on December 5, 1995 by Javier Solana.