The 51-year-old House star will front a campaign for the brand's Men Expert line of cosmetics, following in the footsteps of Gerard Butler and Patrick Dempsey.
Speaking about his new appointment, the British actor joked that he thought the company had got confused when it first asked him to become an ambassador.
In a press release to The Telegraph, he said, 'At first I thought it was a mistake but then I realized that L'Oreal wasn't looking for models, but real people with strong personalities, who are worth it... and who aren't afraid to proclaim that using cosmetics can be a very masculine decision after all.'
But L'Oreal Paris' global brand president, Cyril Chapuy, praised him for being, 'the perfect example of a modern man - genuine, uninhibited, strong and willing to pursue his passions to the end.'