The Black Eyed Peas singer gave birth to the couple's first child - a son named Axl Jack Duhamel - in August, but it appears the couple are ready to add to their brood already.
Gushing about his newborn son to Access Hollywood, Josh revealed: ''He's a really good little baby, which means the second one will be a holy terror!''
Quizzed if that meant they are looking to have another child, the 'Transformers' hunk added: ''Of course! Yeah, we've gotta move fast.''
For now, however, Josh, 40, and Fergie, 38, are enjoying being parents to little Axl.
The star said: ''It's the best thing ever. The best thing that's ever happened to me. It's fantastic. We're beyond happy.''
Josh recently praised his wife, saying she looks better than ever since giving birth.
He enthused: ''She is doing so great. She really is. She is happy. She looks amazing ... three weeks ago she gave birth and she looks probably better than she did before. I don't know if it's because of what she's been eating or what, she looks really, really great.''
His new album Underneath It All is out now.
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