The singer announced the baby news by posting a Halloween-themed home video, in which he and his wife Giovanna carved pumpkins around their kitchen table, online.
At the end of their craft session, the couple switched off the lights and turned their pumpkins around to reveal the message "We're having a baby."
The Obviously hitmaker captioned the short film with the post, "Sometimes the best way to say something is with a pumpkin... and a song."
The video ends with a scan of the baby - the couple's first - with a caption which reads "Arriving 2014".
The MCFly star has since thanked fans for their well wishes, tweeting, "Thank you very much for all the lovely messages. We couldn't hide it any longer... literally."