His diplomatic career started in 1899 when Čolak-Antić was appointed Secretary of the Serbian Representation in Sofia then Minister Plenipotentiary to the Principality of Bulgaria at a time of turmoil in neighbouring Turkish provinces; he expressed concerned about the secret talks happening between the Bulgarians and the Ottomans regarding the unrest in the region of Macedonia, bypassing the three other members representing the different communities Serbian, Greek and Vlach. His mission ended in 1903. After the change of dynasty and the coronation of Peter I of Serbia, on 21 September 1904, Čolak-Antić became actingMarshal of the Royal Court of Serbia, a position he will occupy until 1907 while still executing diplomatic missions around Europe. His next appointment was in Cairo where he served as ambassador from 1908 until 1912, in Egypt he started a lifelong friendship with French Egyptologist Gaston Maspero, who served as director of the Egyptian Museum in Cairo, Maspero mentioned Čolak-Antić multiple times in his memoirs. He was deputy and ambassador in many European capitals, most notably in Sofia, Kingdom of Bulgaria, starting in the period preceding the First World War until the invasion of Serbia by the Central Powers in November 1915. In a telegram dated 1 July 1914, Čolak-Antić warned Prime MinisterNikola Pašić that through a loan offered by the German Empire, the Bulgarian government was bound to the camp of the Triple Alliance. In October 1915 when Serbia was attacked and invaded by the combined armies of Germany, Austria-Hungary and Bulgaria, Čolak-Antić returned home to volunteer and took part in the retreat through Albania to Corfu where he joins the Serbian Government. He relocates to Salonika with the rest of the army and where his brother Vojin, now Colonel, is commander of the 3rd Serbian Cavalry Brigade. After the war and the ensuing reshuffle he became Ambassador of the new Kingdom of Yugoslavia in Sweden, taking residence in Stockholm on 18 February 1918 staying until 1920. On 3 March 1920 Čolak-Antić was envoy extraordinary then ambassador to Romania, he is based in Bucharest where he represented the kingdom in the talks of the Little Entente with Czechoslovakia and Romania in order to build a common defense against Hungary. In 1935 he goes back to Yugoslavia after being appointed Marshal of the Royal Court, he remained in that capacity until 1941.
