Of her childhood in Belfast, Malcomson recalls a constant state of violence and strife, during which “people’s spirits were very intensely alive. What better preparation can you have for acting?” Her first stint before the camera was when director Michael Almereyda cast her in the award-winning experimental film, Another Girl Another Planet. Later that year, writer/director Kevin Jarre cast Malcomson as Allie Earp in Tombstone.
There followed notable performances in Steven Spielberg’s A.I; Artificial Intelligence and in Frank Darabont’s The Green Mile, as well as in Michael Almereyda’s Hamlet. HBO's Deadwood provided Malcomson with a new opportunity to carry a character forward over a long period of time.
Malcomson worked on Lost, ER, Criminal Minds, Cold Case, HBO's John of Cincinnati, Law & Order:SVU, CSI, Fringe, Caprica, Lie to Me and Private Pactice. Most recently she played Katniss’ (Jennifer Lawrenc) mother in the Hunger Games movie franchise and has been announced as Female Lead In Showtime’s Ray Donovan Drama Pilot.