The Love Actually star took to her Twitter.com account on Thursday (13Sep12) to make the announcement, writing, "Happy news! James + I are delighted to announce we're expecting a baby!"
Thornton, who has starred in British soap opera Emmerdale, also tweeted fans, adding, "Happy news! Jo + I are delighted to announce we're expecting a baby!"
The pair wed in 2003 after working together on the BBC TV adaptation of Charles Dickens' David Copperfield.