The BBC released a brief video message from the former Doctor Who actor after he triumphed in the prestigious category at Wednesday night's (January 22) ceremony.
National Television Awards 2014 - red carpet pictures
National Television Awards 2014: Live blog
"Thank you for this wonderful, marvelous award," he said. "It's an honour to be in a category with such fine, esteemed [and] wondrous actors."
The star continued: "I'm sorry I can't be there to accept it in person. I would have, but I'm doing a play… Thank you to everyone who voted.
"You made my time on Who the best and brilliant and the most audacious part of my career to date. I am forever grateful."
Smith exited Doctor Who at Christmas after four years as the Time Lord, and has been succeeded by Peter Capaldi.
The National Television Awards are airing from the O2 Arena in London on ITV.
Watch Khali Best talk to Digital Spy at the National Television Awards about his time on EastEnders and working with Danny Dyer: