
The star, 34, has announced she is expecting her first tot with actor husband Alexis Denisof next spring, according to People.com.
Hannigan met the 42-year-old on the set of cult TV series Buffy The Vampire Slayer during the 1999/2000 season. Denisof played Wesley Wyndam-Pryce in the show.
In 2006, the actor also joined Hannigan on How I Met Your Mother, playing a recurring role, Sandy Rivers.
The pair married in October 2003 and currently reside in Santa Monica, California.