Fergie gave birth to the couple's first child named Axl Jack Duhamel in August, but it appears the couple are ready to add to their brood already, reported Access Hollywood.
"He's a really good little baby, which means the second one will be a holy terror," Duhamel said.
Asked if they are looking to have another child, the "Transformers" star added, "Of course! Yeah, we've gotta move fast."
For now, however, 40-year-old Duhamel, and Fergie, 38, are enjoying being parents to little Axl.