The full lineup of John Power, Liam 'Skin' Tyson, Peter Wilkinson and Keith O'Neill will play a number of yet-to-be announced tour dates to mark the anniversary.
Frontman Power told NME: "I know it's been nearly a decade but everything feels alright. I'm in a good place at the minute so I rang the lads each individually and told them I feel like going out again with the band.
"For me to have rang the lads and for the lads to have come and sat in the same room as me is unbelievable because a few years ago I would have laughed. But now something musical is rising inside of me."
He added: "Five years ago I couldn't bring myself to play them songs, it would have made me vomit.
"I just couldn't go near them, I felt like I'd lost the connection and wrote this other stuff, and that was where I was at. But something's changed now, I feel fond of them again, and I'd forgotten how anthemic they were."
Since Cast split in 2001, Power has released three solo albums and briefly rejoined his former La's bandmate Lee Mavers for a number of live dates.