Palin welcomed a daughter, Sailor Grace, on December 24.
The former reality TV star announced the big news on Instagram the day her newborn arrived.
"My sweet Sailor Grace was born yesterday, our family couldn't be more complete," Palin captioned a photo three days ago of herself cradling and smiling at her baby girl.
In a black-and-white image, Palin's son Tripp was meeting Sailor for the first time.
"My heart just doubled," she wrote.
The 25-year-old former Dancing with the Stars contestant revealed in June she was pregnant, one month after ending her engagement to Marine Dakota Meyer. The couple split just a week before they were going to tie the knot.
Meyer also took to social media to express his excitement over being a father.
"Best Christmas present ever!! I could not be more proud of this little blessing," Meyer captioned a photo of his daughter on Thursday.
Palin decided to reveal her baby's name last month, but only because she didn't want people to accuse her of copying the former The Hills star Kristin Cavallari, whose latest addition is also named Saylor.
"When you find out @kristincavallari named her baby the exact name you are naming yours. What a weird coincidence," Palin joked on Instagram at the time. "Congrats on your new bundle, and I do love her name.. Still naming my baby girl Sailor!"
Palin competed on the eleventh season of Dancing with the Stars back in 2010 and reached the finals with pro partner Mark Ballas, finishing in third place. In November 2010, she appeared on TLC's Sarah Palin's Alaska documentary.
Palin then starred in Bristol Palin: Life's a Tripp on Lifetime in Summer 2012. She most recently competed on Dancing with the Stars' Fall 2012 All-Stars edition. Palin was sent home in the fourth week of the fifteenth-season competition.