Born in Nucet, Dâmbovița County, went to school in Pitești, and then at the Saint Sava National College in Bucharest. From 1922 to 1926 he attended the Faculty of Law of the University of Bucharest. Antonescu made his living as an attorney before becoming the Minister of Foreign Affairs to Prime Minister Ion Antonescu (to whom he was not closely related) in 1940. Antonescu was initially not an extremist or supporter of the Iron Guard, whose leaders held prominent positions in Ion Antonescu's government in 1940-1941 ("see National Legionary State"); in the 1930s, he was a member of the National Liberal Party-Brătianu.