Mona Ali Khalil obtained a BA and an MA in International Relations from Harvard University in 1988 and a Masters in Foreign Service and a Juris Doctorate from Georgetown University in 1992. She is an Affiliate of the Harvard Law School Program on International Law and Armed Conflict.  

She served in the UN Office of the Legal Counsel (UNOLC) from 1993 to 2015 advising the Secretary-General, the Security Council (UNSC) and the General Assembly on a broad range of legally complex and politically sensitive matters relating to the UN's collective peace and security efforts -- peacekeeping, sanctions, disarmament and counter-terrorism. 

During her early service in UNOLC, she appeared before the International Court of Justice on a landmark case involving the UN human rights special rapporteur on the independence of judges and lawyers. She also advised the Rome Conference which adopted the Statute on the establishment of the International  Criminal Court  and assisted in the election of its judges. She also undertook special assignments relating to the Lockerbie incident and the lead up to and aftermath of the 2003 Iraq War.

Between 2005 and 2009, she was seconded to the Office of Legal  Affairs, of the International Atomic Energy Agency where she advised on nuclear security and counter-terrorism as well as the UNSC non-proliferation sanctions regimes. 

Between 2010 and 2015, she served as the head of the legal team supporting the UN peacekeeping operations including their rules of engagement and  use of force to protect civilians. She also served as the legal adviser to the Security Council's various Chapter VII sanctions regimes. She undertook several special assignments including as Legal Adviser to the UN Mission to Investigate Allegations of the use of Chemical Weapons in the Syrian Arab Republic and to the Joint OPCW-UN Mission for the Elimination of the Syrian Chemical Weapons Program.

From 2015-2017, she served as a Legal Advisor with Independent Diplomat, the international diplomatic advisory group, where she promoted inclusive diplomacy and the rule of international law through integrated strategies to achieve peace and justice. 

She lectures regularly at Harvard University, Columbia University and Georgetown University.  Her chapter on the “Legal Aspects of the Protection of Civilians in UN Field Operations” appears in The Protection of Civilians in International Law published by Oxford University Press in June 2016. Among other opinion pieces, she has published  “ The UN’s Three Main Bodies Are Failing to Do Their Jobs ” and "The World Needs Robust Peacekeeping not Aggressive Peacekeeping" and "Restoring the Values and Spirit of the International Civil Service".