[1][2] Born in the Austro-Hungarian capital Vienna, he was a member of a Croatian family ennobled in 1911.

His paternal grandfather Josip Tončić-Sorinj (1847–1931) had been governor in the Kingdom of Dalmatia, his father served as consul in Jeddah.

During World War II, he taught languages in a signal corps of the Luftwaffe.

From 1949 to 1966, he was member of the Austrian National Council parliament for the ÖVP, from 1966 to 1968 he was foreign minister in the cabinet of Chancellor Josef Klaus.

Relying on the 1946 Gruber–De Gasperi Agreement, Minister Tončić-Sorinj played a vital role in the negotiations with Italy over the autonomy of South Tyrol.