While rumours have been circulating for months, US Weekly magazine appeared to confirm the news on Friday (20 November).
Singer-actress Amelia, 33, has been spotted with a growing tum over the past few months sparking hopes of good news for the pair.
Fifty Shades Of Grey star Jamie and Amelia already have a daughter called Dulcie, two.
After getting engaged in November 2012, the couple married in April 2013.
They said their vows at Orchardleigh House in Somerset after six years of dating.
Last year, The Fall actor spoke candidly about fatherhood in an interview with British Vogue.
He said: "I love fatherhood. These last couple of years have been quite something. But we're enjoying it."
On another interview earlier this year, Jamie added: "It's the best thing that has ever happened to me, and to us. It's an extremely joyful situation and every day seems to get better. I know it's my most important role in life."
Jamie and Amelia have not confirmed the news of their second pregnancy themselves.
Brit Jamie is set to reprise his role as Fifty Shades Of Grey's Christian in 2016.
Speaking to People magazine recently, he said: "I'm looking forward to embodying Christian again – and getting a chance to show more of him."
For exclusive competitions and amazing prizes visit Reveal's Facebook page NOW!