The former Doctor Who actor revealed that his wife Georgia Moffett was pregnant with their second child together on last night's Jonathan Ross Show.
"It's lovely, very lovely. It's exciting," he told host Ross.
Tennant and Moffett previously welcomed their first child Olivia back in April 2011.
The Scottish actor later adopted Moffett's then-10-year-old son Tyler in March last year.
The couple married in an intimate London ceremony in late December 2011.
Tennant will next be seen starring in BBC Four drama Spies of Warsaw on Wednesday, January 9 at 9pm.
Watch a trailer below for the show below: