Miroslav Lajčák started his diplomatic career at the Slovak embassy in Moscow and served there between 1991 and 1993. After his return to Slovakia, he was twice appointed Director of the Office of the Minister of Foreign Affairs as well as Director of the Office of Prime Minister (1994).
His professional career also includes the posts of Slovak Ambassador to Japan; Assistant to the United Nations Secretary General Special Envoy for the Balkans; and Ambassador Extraordinary and Plenipotentiary of the Slovak Republic to the Federal Republic of Yugoslavia (later Serbia and Montenegro), Republic of Albania and the Former Yugoslav Republic of Macedonia residing in Belgrade. Further, among his diverse roles are the positions of Personal Representative and European Union High Representative for Common Foreign and Security Policy to facilitate the referendum on the independence of Montenegro as well as High Representative/European Union Special Representative for Bosnia and Herzegovina in Sarajevo.
Since 2005, he has been the Head of the Secretariat for the Organization of the Summit of the Presidents of the Russian Federation and the United States of America in Bratislava.