Corrigan was born into a Roman Catholic family in Belfast. She was the second child of seven (five girls and two boys). She attended Catholic schools until the age of 14. She then found a job as a secretary.

Corrigan became active with the peace movement after her sister, Anne Maguire's 3 children were run over and killed by a car driven by Danny Lennon, an IRA man who was fatally shot by British troops while trying to make a getaway. Anne Maguire later committed suicide.

Betty Williams, a former member of the IRA herself, despite a Protestant father and a Protestant husband, had witnessed the event, and soon after the two co-founded Women for Peace which later became the Community for Peace People. By the end of the month Betty and Mairead managed to get 30,000 women on the streets of Belfast petitioning for peace between the republican and loyalist factions. She believed the most effective way to end the violence was not violence but re-education).

However, the venture ultimately petered out due to in large part to objections from Catholics that the Peace People were focusing entirely on republican violence and ignoring loyalist and state violence by the British security forces.

She received the Nobel Peace Prize along with Betty Williams in 1976 for their efforts. They were criticised for deciding to keep the prize money for themselves.

In 1981 she married Jackie Maguire, who was the widower of her late sister, Anne. She has three step-children and two of her own, John and Luke.

In 2004 she went to Israel and welcomed Mordechai Vanunu upon his release from prison, where he had served an 18-year prison sentence for disclosing Israel's nuclear secrets.

She is a member of the pro-life group Consistent Life which is against abortion, the death penalty and euthanasia.