Beginning her career in the New Zealand Ministry of Foreign Affairs, including as a delegate to the United Nations in New York,[4] Beagle worked across the peace and security, human rights, development, management and gender sectors.
As Assistant Secretary-General and Deputy Executive Director of UNAIDS, Beagle played a leading role in the development of the UNAIDS Strategy 2016-2021, the first UN system strategy to be fully aligned with the Sustainable Development Goals (SDGs) following their adoption in September 2015, after a broad consultation in all regions and virtually. While working for UNAIDS, Beagle led a programme to increase the number of women working in senior positions across the agency.[6] In 2017, she was investigated over harassment claims; the UNAIDS executive director, Michel Sidibé, eventually recommended the case be closed following an internal investigation that found the allegations were unsubstantiated.[7] Then, on 10 February 2020 the Administrative Tribunal of the International Labour Organization (ILOAT), during its 129st session, in case 4241, ruled that claims of harassment were indeed substantiated and that UNAIDS "...incurred liability towards the complainant on account of this harassment...".[8]
Beagle also served as Deputy Director-General of the United Nations Office at Geneva (UNOG).[4]
Beagle has also held senior positions in the Executive Office of the Secretary-General, the Office of the Administrator of UNDP, and the Department of Political and Security Council Affairs. She has represented the Secretary-General as spokesperson for the system in the General Assembly, International Civil Service Commission (ICSC) and the Pension Board, and as a member of the Boards of the United Nations System Staff College and UNITAR. She also served as the Chair of the Assistant Secretary-General Advisory Group of the United Nations Development Group.[2]
In November 2017, Beagle was appointed to lead the United Nation's High-Level Task-Force on Sexual Harassment, which is charged with improving support for sexual harassment victims and strengthening internal investigations.[9] In May 2018, she launched the organization's screening system to prevent former employees guilty of sexual misconduct from finding new jobs with its agencies or other charities.[9]
In 2019, Guterres appointed Beagle as his Special Adviser on System-wide Implementation of Chief Executive Board (CEB) decisions.[2]
Since 2020, Beagle has been serving as Director-General of the International Development Law Organization (IDLO), succeeding Irene Khan.[10]