Byrne has held a number of senior positions including (current) Acting Director of the Daughters of Charity Child and Family Service, Head of Communication and Advocacy at Depaul Trust (Homeless Service) (2003–2006), and Chair of the National Council on Ageing and Older People.
[1] She has also worked as a volunteer with the SATU (Sexual Assault Treatment Unit) team from Dublin Rape Crisis Centre.
Byrne began her career as a secondary school teacher and also ran language programmes between Irish students and young people in France, Germany, Spain and Italy.
She was chairperson of the visiting committee for Dóchas Centre women's prison, at Mountjoy, Dublin, until her term ended in 2011.
In 2009, Byrne drew criticism when she suggested it was "unpatriotic" for the Republic's citizens to go shopping in Northern Ireland.