He will join the company from 19th August 2019 and will play the lead role of Dewey Finn.
Sullivan rose to fame as part of pop group Popstars and has gone on to enjoy a successful career in theatre and television.
His credits include Years and Years (BBC One), Gavin and Stacey (BBC One) We Will Rock You (Dominion Theatre) and Grease (Piccadilly Theatre).
Noel Sullivan said: “It’s been a lifelong ambition of mine to perform in a musical by Andrew Lloyd Webber. I have been a huge fan since I was a child and to get the opportunity to work on such an incredible production is absolutely a dream come true.
"I loved School of Rock the movie and this hilarious musical doesn’t disappoint. I look forward to not only taking on one of my most challenging roles to date but also working alongside some of the most talented kids in the country. I’ve been in some great bands before but this one is really going to take some beating!”
Sullivan will lead the new adult cast with Laura Tebbutt as Rosalie Mullins, Mark Anderson will take over the role of Ned Schneebly from Alan Pearson from 8 October 2019, Rebecca LaChance continues as Patty Di Marco and Jake Sharp will play Dewey Finn at certain performances.
The remaining adult cast comprises Keisha Amponsa Banson, Ryan Bearpark, Rob Falconer, Kelly Hampson, Suzie McAdams, Richard Morse, Jayde Nelson, Andy Rees, Alex Tomkins, James Wolstenholme and Benjamin Yates with swings Jessica Kirton, Paul Kemble, Billy Mitchell, Catherine Morris, and Andy Prosser.
Based on the hit film, School Of Rock follows Dewey Finn, a failed, wannabe rock star who decides to earn a few extra bucks by posing as a substitute teacher at a prestigious prep school. There he turns a class of straight-A students into a guitar-shredding, bass-slapping, mind-blowing rock band.
School Of Rock - The Musical is currently booking until January 2020 at the Gillian Lynne Theatre.