Harris, 37, and his longtime partner David Burtka are expanding their family, the How I Met Your Mother actor confirmed Saturday.
"So, get this: David and I are expecting twins this fall," Harris revealed on Twitter. "We're super excited/nervous/thrilled. Hoping the press can respect our privacy..."
According to E! Online, which was first to report the news, the couple are going to become parents with the help of a surrogate.
Harris and Burtka appeared to be getting into the spirit of their upcoming role as parents on Saturday: They were photographed at Disneyland.