The Irish singers caught up for a drink after appearing on the entertainment show on Saturday (15 March), which was a St. Patrick's Day special.
Posing for a selfie, Kian tweeted: "Great seeing @nickybyrneoffic last night for @itvtakeaway and a few Guinness's afterward."
Meanwhile, dad-of-three Nicky jokingly said: "Met some bloke that I used to know too.. Are we WEST or were we the LIFE @itvtakeaway @KianEganWL."
Westlife enjoyed 14 successful years in the pop charts since their formation in 1998 and continued as a band despite Brian McFadden's departure in 2004. They eventually split after a greatest hits album and farewell tour in 2012.
It proved to be a night of celebrations for Kian and Nicky, as they later partied with X Factor stars John & Edward, who had also appeared on the show.
We're sure Kian didn't party too late though, as he had to attend a signing for his debut album 'Home' the next morning.
The 33-year-old had fans queuing up to see him at Dundrum's HMV store in Dublin, Ireland. During the event, Kian tweeted: "It's Going crazzzzzyyyyy down in #HMVdundrum in Dublin. WOW!! Best fans!"
Dad-of-one Kian, who is married to Big Reunion star and former Hollyoaks actress Jodi Albert, unveiled the music video for his new single two weeks ago, which is also called 'Home'.
The song, which is a cover originally sung by 2006 American Idol finalist Chris Daughtry, is the lead single to be taken from Kian's album.
In the visual, Kian looks back on family life and reflects on his time in I'm A Celebrity... Get Me Out Of Here!, in which he was eventually crowned the winner.
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Watch Kian's music video for 'Home' below: