Harris, 41, turned to Twitter to announce news of his marriage to fellow actor David Burtka, 39, saying the couple wed in Italy over the weekend.
— Neil Patrick Harris (@ActuallyNPH) September 8, 2014
The exact location of the wedding was not announced, although actress Kelly Ripa told ABC News the ceremony was held in a rented castle.
Singer Elton John performed at the reception and director Pam Fryman officiated, People magazine said.
The couple announced their secret five-year engagement in 2011, less than a year after the birth of their twins. Just weeks ago Harris dispelled rumours that he had split from Burtka, posted a photograph of the happy couple on Instagram.
Gay marriage is banned in Italy, meaning the wedding will not be legally recognized in the country.