"I'm telling this for the first time, it feels so strange," she told Colbert in a video. "I gave birth to a baby boy on September 3."
Colbert acted surprised by the announcement, saying, "No one even knew you were pregnant!"
"I know," Kaling laughed. "This is news to a lot of people, it's true."
Kaling added that she named the little baby Spencer.
The tot joins her daughter, Kit, 2; Kaling has never publicly revealed the child's father.
The Mindy Project star has opened up in the past about motherhood, saying she wanted to follow her own late mother, who died of pancreatic in 2012, for inspiration.
"My mom was incredibly fierce and so devoted to us. Just loved us and really wanted us to be happy no matter what we did," she told Sunday Today's Willie Geist. "My career choice was not something that she was familiar with and she was just so supportive of that. And if I could give that to my child, just that open-mindedness, I'd be so happy."
Prior to motherhood, the star admitted that having children was on her mind.
"I think I've decided that unlike everything else in my life, I'm going to be fast and loose about kids," she said. "I'm going to not actively plan, but if it happens, it would happen."
She continued, "I'm not cavalier about who I would have a kid with. But the thing I ask every parent that I really admire, the one comment they all have is that they wish they had kids earlier."
The Never Have I Ever show creator has been candid about how important her family is to her. So much so, her father, Avu Chokalingam, has visited his granddaughter every day since she was born in 2017.
"Sometimes it’s to push her on the swing for 45 minutes, sometimes it’s a stroll around the block to look at snails," Kaling said in a lengthy Instagram post in June. "Even when I moved to New York or London for work, he Skyped with her on the phone or flew out to see her in person."
She added that at the height of the coronavirus epidemic, Chokalingam would meet up with Kit outside with puzzles and Indian food.