"The Timberlakes are ready!!! GO GRIZZ! #GritNGrind #Playoffs #BabyGrizzROAR," he captioned the photo.
It is also the first time Jessica has been pictured since the birth.
The 33-year-old looks stunning in the snapshot with no make-up, wearing a baseball cap and a black top showing her blue lace bra underneath.
The couple's rep confirmed the arrival of Silas Randall Timberlake on April 11 and told People that 34-year-old Timberlake is "ecstatic," and both mother and baby are doing well.
Silas was the middle name of Timberlake's grandfather, and Randall is the name of his father, as well as the singer's own middle name.
The Suit & Tie hit-maker finally confirmed Biel's pregnancy in January after months of keeping it under wraps.
On his 34th birthday, he shared a snap which showed him kissing his wife's baby bump, along with the caption: "Thank you EVERYONE for the Bday wishes! This year, I'm getting the GREATEST GIFT EVER. CAN'T WAIT."
The 'N Sync star also revealed that the couple chose to wait until their baby's arrival to find out the sex.
Timberlake and Biel married in October 2012 after five years of dating.
- Daily Mail