The two are engaged after the Blink-182 drummer proposed on a beach in Montecito, California on Sunday, according to TMZ, which first reported the news.
Barker, 45, got down on one knee within an extravagant floral arrangement on the sand at a beachside hotel.
Kardashian, 42, confirmed the news on Instagram with a picture of the moment, captioned “forever.”
It will be the first time the reality star gets married. She shares three children with her ex-boyfriend, TV personality Scott Disick.
Barker was previously married to model Shanna Moakler.
The couple have been dating since the start of this year and first announced they were seeing each other in February.