James made it through on the public vote while Jodi Bird and dance troupe The Addict Initiative both made it to the judges vote, before Amanda Holden picked Jodi, while David Walliams, Simon Cowell and Alesha Dixon all picked The Addict Initiative allowing them to go through to the final.
James and The Addict Initiative will now perform on Saturday's final where the winner will be decided, and will go on to perform for the Queen at the annual Royal Variety Performance later in the year.
James Smith, The Addict Initiative, and Jodi Bird
"It's amazing, we worked so hard", The Addict Initiative said, while James added: "I'm feeling good!"
Nine acts took to the stage on Tuesday in the second semi-final, including two dance acts, a trio of puppets, four singing acts, a BMX group and a comedian.
The three finallists - The Addict Initiative, 16-year-old singer Jodi Bird and 15-year-old guitar player James Smith -all received the best reviews, while Kony Puppets were stopped halfway through when all four judges pressed their red buzzers.
Hosts Ant and Dec opened the show before first act Mini Moves, a five-piece dance group from Glasgow made up of young girls took to the stage. Dancing to a mix that included Beyoncé and Little Mix, the group had energy and looked to be having great fun as they opened the show.
"It's amazing, we want to do it all over again", the group of girls told Ant and Dec.
Ed Drewett, a singer-songwriter who has wrote songs for musicians including One Direction and Olly Murs, wowed the crowds with a performance of his own song, while third act, the Bolddog FMX Team, a group of four freestyle motocross drivers showed off their bravery and skills.
Jodi Bird gained the night's first standing ovation, which included David Walliams and Amanda Holden, with a stunning performance of the Oscar-winning song Let It Go from Frozen. Girl band Sweet Chix sang a version of Taylor Swift's I Knew You Were Trouble but were the first act to gain mixed reviews, with both Simon and Alesha revealing the group had disappointed them.
Comedian Ricky K got the first buzz of the evening from Simon Cowell, who later said "I like you... but I'm being honest, the first time it was fresh and different, the second time, the script wasn't funny.", but dance troupe The Addict Initiative received the best comments of the night, with Simon describing them as the best dance act since Diversity, who won the show in 2009.
Kony Puppets were denied the chance to finish their act when all four judges pressed their red buttons, and described the act as unfunny, but James Smith, who sang an acoustic version of Gnarls Barkley's Crazy was called "super super talented" by Alesha, and a "confident performance" by Amanda, while Simon added "it was one of the best performances of the series so far".