He was born in Rome, where his family held (and still hold) one of the most famous cafés, Giolitti, where he also worked for a while.
After World War II, Giolitti moved to South America, where he worked for Editorial Lainez and Columba of Buenos Aires.
After three years in there he was able to move to his original destination, the United States; there he became a mainstay of Western/Dell Publishing, penciling numerous characters, including Indian Chief, Sergeant Preston of the Yukon, Abraham Lincoln: Life Story, Tonto, Cisco Kid, Turok, and Gunsmoke.
After obtaining American citizenship, in 1960 he returned to Italy, from where he continued to collaborate with Western and other US and British publishers.
Series he worked on in this period include Gold Key Comics' Star Trek and Edgar Rice Burroughs' Tarzan of the Apes.