When they first met, James was in the process of separating from his first wife, Anne-Marie Duff.
James and fellow actor Anne-Marie were married for 11 years, and share a nine-year-old son, Brendan.
James and Lisa were recently spotted in Philadelphia, and Lisa appeared to be wearing a wedding ring.
According to Daily Mail, director Jamie Lloyd, who is a close friend of the Glasgow-born actor, said he believes the pair have married in private.
Jamie was overheard at an industry party in London last week describing how Lisa visits James often during rehearsals.
He then went on to refer to Lisa as James' "wife" and said they married "recently".
The publicity-shy couple didn't go public with their relationship until two months after James and his ex-wife's divorce was finalised, when James shared a snap to his Instagram account.
Congratulations to the happy couple!