The former 'Glee' actress and husband Tyler Hubbell - who already have son Elijah, 11 months, together - are expecting their second child, the 28-year-old revealed on her Instagram page.
Heather showed off her tiny baby bump from the side as she posed alongside a large blue ruler which read 'The Growing Hubbells'.
She also used the hashtag TheGrowingHubbells to caption the picture.
Among the first to offer their congratulations to the couple was Heather's former 'Glee' co-star Naya Rivera, who is currently expecting her first child with husband Ryan Dorsey.
She tweeted: "SO exciting! Congrats @HeatherMorrisTV #thegrowinghubbells"
After welcoming Elijah into the world, Heather - who married childhood sweetheart Tyler in May - decided not to return to 'Glee' for the fifth series, though she reprised her role as Brittany Pierce for the 100th episode and the programme finale.
She has previously spoken of how much she adores parenthood. She said: "I love being a mom. Boys are the greatest."