“I meannnnn my baby Psalm is so sweet!!!” she captioned the photo, which had more than 5 million likes as of Thursday afternoon.
“Little tiny goose bunny,” commented one of Kardashian’s sisters, Kourtney, in response.
“Lucky,” wrote singer Gwen Stefani.
“Perfect angel baby,” wrote one person in response.
“Sooooo sweet! What a gorgeous baby,” said another.
The “Keeping Up with the Kardashians” star and her husband Kayne West welcomed Psalm, the couple’s fourth child, in May via surrogate.
"He’s here and he’s perfect!" Kardashian wrote on Twitter when she announced the news.
The rapper and the makeup mogul are already parents to North, 6, Saint, 3 and Chicago, 1. Kardashian announced she was expecting baby number four in January and has been open about her decision to use a surrogate because of health complications.
“Last pregnancy, I had a condition called preeclampsia, which is a serious condition you can get during pregnancy; often, the only way to get rid of it is to deliver early to protect yourself and the baby. Only about 5 percent of women get this. Lucky me! It causes your body and face to swell, and that was very uncomfortable for me. I had early-onset preeclampsia and I had to deliver at 34 weeks, almost six weeks early,” she wrote on her website at the time.
"We induced my labor and I had North soon after. Right after delivery, the placenta usually then comes out. Mine did not. My placenta stayed attached inside my uterus, which is a condition called placenta accreta. This is a high-risk condition that happens when the placenta grows too deeply into the uterine wall."
Due to the serious risk, Kardashian decided not to carry her third and fourth children.
Fox News' Jessica Napoli contributed to this report.