The bassist and his actress wife Erin are expecting a sibling for their two-year-old daughter Coco.
Kanal announced the news on Monday (22Jul13) in a post on his Twitter.com page, which reads: "Erin, Coco and I are ecstatic to announce that our family is growing!"
He also shared a cute photo of Coco looking up to her mother's bulging belly.
Kanal, who previously dated bandmate Gwen Stefani, wed Erin in 2010.
The musician's child will be the latest addition to a growing No Doubt family - Stefani has two sons with rocker husband Gavin Rossdale, drummer Adrian Young and wife Nina have a boy and a girl and Tom Dumont has three kids - Koa Thomas, Rio Atticus, and Ace Joseph.