[citation needed] Mrkić started his diplomatic career soon after graduation, with a job at the Federal Ministry for Foreign Affairs of Yugoslavia.

[citation needed] Mrkić continued his diplomatic service in Brussels, where he served as the Minister Counselor for the Yugoslav mission to the European Community between 1990 and 1992.

Starting in 2004, Mrkić joined a group of ambassadors for special and ad hoc duties in the Ministry of Foreign Affairs of the then Serbia and Montenegro.

[citation needed] In 2005, he served as President of the National Commission for the Implementation of the Chemical Weapons Convention, appointed by the Council of Ministers of Serbia and Montenegro.

He explained that a foundation for foreign policy would remain, preserving territorial integrity and sovereignty, and that the priority would be fully-fledged European Union membership.

"[12]He has been nominated by the government of Serbia on two occasions (2017 and 2020) as a member of the National Council for the Coordination of the Cooperation with the Russian Federation and the People’s Republic of China.

Since 2020, Mr. Mrkić assumed the duty of the member of the Editorial Board of the Magazine Napredak (Progress), as Editor-in-Chief of International Affairs.