"I'm pregnant!" she announced Monday on CBS's The Talk, to loud cheers from the audience – though she was only joking.
"No, no, no!" she said. "But my daughter-in-law is!"
Osmond, 53, revealed that her eldest son, Stephen Craig, and his wife Claire are expecting their first child together.
"I'm going to be a grandma!" she beamed. "And I just can't wait. Isn't that fun? So excited."
Craig broke the news to his mother recently on his 30th birthday. "He blew out the candles and then blew me away and said, 'You're going to be a grandma!' So, it's really fun," Osmond said.
As the crowd cheered, Talk co-host Sharon Osbourne – who became a grandmother last year when son Jack's baby daughter was born – was clearly thrilled.
"It is a gift from God," she told Osmond, "and congratulations."