Thousands of the show's fans, who turned up at the Waterfront Hall to catch a glimpse of multi-millionaire music producer Cowell and fellow judges David Walliams, Amanda Holden and Alesha Dixon (right) weren't disappointed as the stars took the time to sign autographs, chat and even take some 'selfies'.
The Belfast spectacular was the first in a packed schedule of auditions to be held across the UK, and marked the first time the show has been to Northern Ireland.
Speaking before the auditions, 54-year-old Cowell said he was delighted to bring the show to the province for the first time.
"I'm excited about it. I like going to places with the show we haven't been before," he said.
"We never were invited before. But finally we were allowed to come, and here we are."
While Cowell was casually dressed for his red carpet arrival, Amanda Holden and Alesha Dixon didn't disappoint fans hoping for glamour.
Amanda was wearing a striking structured grey dress, accessorised with a Union Jack umbrella to keep off the driving rain. Meanwhile, Alesha was wearing an elegant deep navy jumpsuit, with a double breasted coat draped over her bare shoulders.
Around 2,000 spectators packed into the venue to get a preview of the auditions that will not air on TV until the summer.
Rumours that the stars were staying in Malmaison Hotel in the city centre turned out to be false, while the five-star The Fitz-william Hotel said they could not give out details about guests.
Any talent that was found was kept well under wraps, although Cowell did leak some inside information when he tweeted: "Hello. I am in Belfast. Have just seen a cat backstage trying to play the guitar!"
Amanda Holden boasted that the judges had "found some gems", while both Dixon and Walliams thanked Belfast for its support, with Walliams adding: "What a brilliant start to the new series."
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