Simon Cowell, Amanda Holden, David Walliams and Alesha Dixon were joined by hosts Ant and Dec plus the NI audience, as a number of hopefuls took to the stage with dreams of being put through to the next stage of the competition.
The city was on red alert, with many aiming to spot a few of the famous faces prior to the big day and Geordie duo Ant and Dec were caught having a cheeky pint in The Duke of York on Friday.
The pair told UTV they expected Belfast to "set the level" of standard for this year's talent.
Meanwhile, Amanda, David and Alesha arrived in the city on Friday night aboard Simon's private jet.
The man himself did not make it into the city until Saturday, and he quickly took to Twitter to ask: "Where can I get a slice of toast?"
This prompted his fellow panelist David to take the opportunity to hurry the boss up as he responded: "Can you get a bloody move on? It's three o'clock in the afternoon!"
It's always a good vibe in Belfast.
When the judges did finally make it to the venue, they took some time to chat with fans and pose for pictures, with Simon sporting his trademark sunglasses, despite the rainy weather.
"We have got to find someone good," he told UTV. "I have no idea who is going to come in or what is going to happen and you have just got to find one good person or one good thing.
"I don't think we had enough animals last year."
Giving his professional opinion on what act would be a winner, the music mogul said he thought there was "a gap in the market" for a cat who could play the guitar.
He later tweeted from the Waterfront: "I am in Belfast. First day of Britain's Got Talent. Have just seen a cat backstage trying to play the guitar!"
This is the first time the Britain's Got Talent auditions have been held in Belfast.
"I'm so pleased we have come to Belfast," said Alesha.
"It is fantastic for the show and it's fantastic for Belfast and I'm open minded about what I am going to see today.
Obviously we have to see some Irish dancers, it would be wrong not to!
"And hopefully someone will have the luck of the Irish and get through to the semi-finals and final and get to represent Ireland, which is what it is all about."
The singer also had advice for those who were auditioning for the panel.
"Four minutes could change your life so go for it; you have got nothing to lose.
"You don't want to go away from the auditions thinking "what if?" you want to make sure that you nail it."
The new series of Britain's Got Talent will be broadcast on UTV in May.