They had been due to play the first of three gigs at the SSE Arena on Tuesday, reported BBC News.
The cancellation announcement was made at about 9 pm, when most of the audience was already inside the venue.
Disappointed fans booed as staff instructed them to leave the venue and one witness said "hundreds" of girls and women had been left weeping.
Concert promoter Aiken PR said: "The show tonight has been cancelled as Liam has taken ill, and whilst not serious, he is unable to perform tonight."
In a statement, the band, who are undergoing a final tour before taking their first break next year since forming on X Factor in 2010, apologised to their fans.
And on his Twitter account, Harry Styles wrote: "Deepest apologies to everyone at the show tonight in Belfast. Very disappointed, but unfortunately these things happen. We're very sorry."
Band mate Louis Tomlinson tweeted: "We're so so sorry for what happened tonight, it was out of our control! Lots of love to Liam and thank you for being so understanding!"
You’ve reached your limit of {{free_limit}} free articles this month.
Subscribe now for unlimited access.
Already subscribed? Log in
Subscribe to read the full story →
Smart Quarterly
₹900
3 Months
₹300/Month
Smart Essential
₹2,700
1 Year
₹225/Month
Super Saver
₹3,900
2 Years
₹162/Month
Renews automatically, cancel anytime
Here’s what’s included in our digital subscription plans
Exclusive premium stories online
Over 30 premium stories daily, handpicked by our editors


Complimentary Access to The New York Times
News, Games, Cooking, Audio, Wirecutter & The Athletic
Business Standard Epaper
Digital replica of our daily newspaper — with options to read, save, and share


Curated Newsletters
Insights on markets, finance, politics, tech, and more delivered to your inbox
Market Analysis & Investment Insights
In-depth market analysis & insights with access to The Smart Investor


Archives
Repository of articles and publications dating back to 1997
Ad-free Reading
Uninterrupted reading experience with no advertisements


Seamless Access Across All Devices
Access Business Standard across devices — mobile, tablet, or PC, via web or app
