Annabelle Pegrum was educated at the Holy Cross College, Woollahra, and graduated with an Honours degree in Architecture from the University of Sydney, winning the Leslie Wilkinson Prize for Design History and Theory.

She was in private practice as an architect before joining the then National Capital Development Commission, where she made a strong impact on the capital works program. She left in 1986 to take up a lecturing position at the University of Canberra but rejoined the ACT Public Service in 1990, and has worked as an architect and town planner with the National Capital Authority.

She is a Fellow of the Royal Australian Institute of Architects, is President of the ACT Chapter and has been a member of the Architects' Board of the ACT since 1992. She has been an Adjunct Professor of Architecture at the University of Canberra since 1999.

Pegrum has held a number of senior executive management positions with the ACT Government, including General Manager of City Operations from 1994 to 1995, Executive Director of the Cabinet and Policy Co-ordination Office in the Chief Minister's Department in 1996, and Chief Executive of the Department of Business, the Arts, Sport and Tourism ACT from 1996 to 1998.

She has described herself as an advocate for the private sector and assisting partnerships to deliver economic and cultural developments for the ACT.

As a departmental head she has been credited with significantly raising morale and refocusing staff.

She was a member of the ACT Centenary of Federation Committee from 1998 to 2001.

In 1998 Pegrum was the Telstra ACT Business Woman of the Year, and won the MobileNet Corporate and Government Award. She received a Centenary Medal in 2003.

She is the mother of two children.