While the couple are yet to officially comment, multiple sources have confirmed the news to US Weekly.
According to Page Six, the 41-year-old German actress has been abstaining from alcohol and opting for loose-fitting dresses on the red carpet.
A black-and-white photo uploaded to Instagram last week also had fans speculating the Inglourious Basterds star was pregnant.
The couple have been together since 2016 after she split with boyfriend of 10 years, Joshua Jackson.
This will be Diane’s first child, however Norman is already a dad to 18-year-old son Mingus Lucien Reedus with supermodel Helena Christensen whom he dated for five years before they split in 2003.