The Westlife singer, 33, enjoyed a drink in the famous coffee chain and treated Koa, who turned two in December, to a beverage too!
But, when Kian posted the adorable snap on his Instagram page, he assured his fans he wasn't giving his son any caffeine!
The current King Of The Jungle after winning last year's I'm A Celebrity... Get Me Out Of Here!, Kian wrote: "Me and Koa enjoying his first Starbucks! Don't worry it's just foamed milk!"
In the picture, Koa has a foam moustache - cute! - and looks chuffed to bits with his very own drink, while proud dad Kian is smiling from ear to ear under a cosy-looking beanie hat.
Koa is Kian's only son with wife Jodi Albert, an actress and singer who will be taking part in the new series of the Big Reunion.
Earlier in the day, Kian told his fans to expect some news next week. He teased: "Got some very exciting news today! All will be reviled next week!"
He also added: "Me and the wife @JodiAlbert just finished our first gig together! Watch @Daybreak on Monday were we will be live with a cool announcement!"
We can't wait to hear what it is...
Can you guess what Kian's exciting news is? Tell us your theories below!