Although the McBusted singer hasn't quite shown us Buddy Bob's face, you can see the baby's tiny hands clutching Fletcher's thumb.
Dressed in a white fleece bodysuit with black stars, it looks as if Buddy has a head of dark hair.
Fletcher's wife Giovanna gave birth to the couple's second child on Tuesday 16 February. They are already parents to two-year-old Buzz.
Announcing the news on Instagram, Giovanna wrote: "What a beautiful day to be born. Welcome to the world Buddy Bob Fletcher."
Fletcher followed the announcement up with a tweet that read: "Completely overwhelmed with love for our second son Buddy, and can’t wait for him to meet his big brother."
Completely overwhelmed with love for our second son Buddy, and can’t wait for him to meet his big brother. Thanks for the lovely messages. X— Tom Fletcher (@tommcfly) February 16, 2016
Since the arrival of Buddy Bob, the singer has been sharing an insight in to how things have changed now they've become a family of four.
Two-year-old Buzz now gets to wear a "big brother" dressinggown.
Family have been visiting with congratulations gifts (including cheesecake).
Fletcher now feels he deserves to wear "both these Daddy pig socks".
There have been some night feeds.
Night feed 🌛👶🏼😴— Tom Fletcher (@tommcfly) February 19, 2016
And a brand-new business idea.
Just realised I can now start a family business called Fletcher & Sons. I’m totally doing that. We’ll be chimney sweeps.— Tom Fletcher (@tommcfly) February 18, 2016