Philomena, the story of an Irish woman’s 50-year search for her son, won the award for best adapted screenplay.
It was partly filmed in County Down and stars Dame Judi Dench and Steve Coogan.
Philomena was co-written by Coogan and Jeff Pope.
Their screenplay was based on the true story of an Irish woman trying to find the son she was forced to give up for adoption.
In his acceptance speech Coogan praised the “real Philomena Lee”.
He said: “Her story has been told and her story finished in the Vatican. She has been heard but there are 60,000 other women who have yet to trace their children, and their story isn’t over.”
The movie has also been nominated for four Oscars, including best picture.