The Take That star will sing two tracks on the new version of Jeff Wayne's 1978 classic LP.
Joss Stone, Maverick Sabre and Alex Clare will also feature on the album, to be released in November digitally and on double vinyl.
Liam Neeson will voice the character of The Journalist, originally played by Richard Burton.
Kaiser Chiefs frontman Ricky Wilson will appear as The Artilleryman, the character he will also play in the upcoming stage show, which kicks off in December.
Barlow will sing as 'The Sung Thoughts of The Journalist' on two of the album's most famous tracks - 'Forever Autumn' and 'The Eve of the War' - originally performed by Moody Blues frontman Justin Hayward.
Barlow said: "I've been a huge fan of the War of the Worlds score since I was a kid, so to be asked to work with the legend that is Jeff Wayne was a real privilege."
Sabre will play Parson Nathaniel, originally played by Thin Lizzy's Phil Lynott, while Joss Stone will voice Beth, originally Julie Covington. Finally, Clare will sing 'Thunder Child', the track first performed by Chris Thompson.
A 3D hologram of Liam Neeson will be used for the upcoming stage show, which will also feature Wet Wet Wet's Marti Pellow.
"I knew and loved the book from when I was a teenager and it was an easy persuasion," Neeson said. "And I bought the album in 1979 when I was working in Ireland. I still have that little cassette."
The original War of the Worlds album has spent over 330 weeks on the UK chart to date, and has reached number one in 11 countries, selling over 15 million copies.
Watch a promo for the live tour below: