 During the 2016 Slovak Presidency, the Council of the European Union did not agree on conclusions on EU enlargement; the "conclusions of the Presidency" which were issued instead of the usual Council conclusions were criticized for their wording and lack of legal value.From May 2016, Lajčák was one official candidate for the Eastern European Group to succeed to Ban Ki-moon during the 2016 United Nations Secretary-General selection; he received two "discourage" votes from the 5 permanent members of the UN Security Council and was not elected.Among other issues, Lajčák, in his candidacy for UN Secretary-General, addressed the issue of sexual exploitation and abuse by UN peacekeepers,

Lajčák also served as President of the 72nd Session of the UN General Assembly from 2017 to 2018 where he advocated for dialogue, strengthening multilateralism and the need to serve all people.