The Girls Aloud star, 32, made the happy announcement on Twitter on Saturday (15 November).
Kimberley simply posted a picture of her manicured hand, with a HUGE diamond sparkler on her ring finger!
Although the photo speaks for itself, Kim added a ring, heart and family emoticons.
Fans were quick to congratulate the star, with many writing: "OH MY GOD." Another added: "awwwwww."
She and former Triple 8 singer Justin have been together for more than 10 years and have always been open about their desire to get married.
In September, they welcomed their first baby together.
Son Bobby Jay was born on the 4 September.
Kimberley announced his arrival online, posting: "Our beautiful baby boy Bobby arrived yesterday afternoon 04/09/14 he's perfect."
She returned to work a month later when she performed at the Specsavers' Spectacle Wearer Of The Year Awards.
A huge congratulations to Kimberley and Justin on their fabulous news!
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See the other celebrity couples who have welcomed babies in 2014:
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