The 20-year-old and her rapper boyfriend Travis Scott are believed to have broken the news to friends earlier on this month at the Day N Night Fest in Anaheim.
TMZ first broke the news, with a report stating that Travis was telling friends his life was about to change.
Another source also informed People that the Keeping Up With The Kardashian’s star is overjoyed at the news.
Kylie only began dating Travis in April following her split from long-term boyfriend Tyga – who shares son King Cairo with rob Kardashian’s ex Blac Chyna.
As news broke of the pregnancy Tyga appeared to comment on the shock news, Snapchatting, then deleting, the comment: 'hell nah that's my kid!'
Not normally one to be shy, Kylie has been unusually quiet on social media lately, refraining from any full body shots, instead posting cropped selfies of her head and shoulders, while skipping any public events.
On Thursday she shared one full-length shot with a group of friends, but hid her body under a baggy T-shirt.