Keeping Up With The Kardashians star and makeup mogul shared the new arrival with a black and white photograph of her newborn's hand.
The snap was captioned with a blue heart and the date of birth "2/2/22", indicating she gave birth to a baby boy. The baby, whose name is yet to be revealed, arrived the day after celebrating elder daughter Stormi Webster's fourth birthday.
The Kardashian clan led the celebratory messages with Kim Kardashian, 41, and sisters Kourtney, 42, and Khloe, 37, leaving brief emoji-filled comments.
Eldest sister Kourtney said, "Mommy of two life", with a heart and two praying hands, while Kim and Khloe left blue hearts and an angel emoji.
Read more on msn.com