The event is taking place on the last day of the festival, Sunday June 28.
Getwestlondon caught up with Richard Hadfield, of Collabro, ahead of the festival.
Richard said: "It's going to be incredible. When I heard I was so excited.
"It just proves that our music resonates with people young and old... It will be a fantastic day.
"[We will perform] some of our covers, a mixture of the first and second albums, and we'll throw in some surprises... Maybe even Let It Go from Frozen!"
Since the band won Britain's Got Talent (BGT) last year, the five-piece musical theatre group have performed at the Royal Variety Show, had a number one debut album Stars, and sold out a 32-date UK tour.
The band have now released a second album Act Two.
Richard said: "There are pop crossovers in the second album. The fans pitched all of the songs... It's what the fans want to hear."
Performing at Hyde Park will be just one of the life-changing concerts Collabro have performed since their BGT win last year.
Richard said: "I had a poignant moment in Brighton; I used to busk for spare change there, and then we performed in the Brighton Centre for 3,000 people.... All of our lives have changed!
"Singing live is what we live for."
Britain's Biggest Family Event this year will be filled with comedy, music and good old-fashioned family entertainment, plus street food to die for!
Headlining the event will be X Factor's Union J; while other acts will include Justin Fletcher, Dick & Dom, Sam & Mark, Horrible Histories, Brainiac Live!, Shaun the Sheep and much more.
And for teens, rising stars from Youtube, including Hazel Hayes and The Mandeville Sisters will be talking fashion, beauty and all things comedy.
There will also be an Urban Area including BMX and parkour.
James King, senior vice-president of AEG Live, said: "The line-up for this year's family content day is our best yet.
"We have gathered together the very best in children's, teen and family entertainment and it is a fantastic way to round off an exceptional two weeks of comedy, music and entertainment."
Dick and Dom said: "We'll be bringing you the biggest names and best acts. It's going to be the best day out for the kids... And you!"
So get your ticket soon and get down to the family event of the year!
Barclaycard presents British Summer Time Hyde Park runs from June 18 - 28.