Adams, 53, is already a father to an 18-month old daughter from Grimaldi. He announced the news on Twitter.
"Alicia's either eaten too much chocolate cake or we're expecting another baby... I think it's a baby,' he tweeted.
A representative for the singer later confirmed it.
"There's another baby on the way for singer Bryan Adams and Alicia Grimaldi. Their daughter, Bunny Grimaldi-Adams, is now 18 months old, and the new baby is due next year."
Alicia, 31, met Adams in 2004 while helping to set up his Bryan Adams Foundation, which provides grants to support vulnerable people.