Fire crews are fighting a fire in the roof of a stable block at the yard in Newmarket. Suffolk fire said all the horses had been led to safety before they arrived.
Forty firefighters are at the scene of the fire, which broke out in the roof of a stable block.
They say they'll be on site for the rest of the day.
Luca Cumani's racing operation has been based in Newmarket since 1976, when he bought the Bedford House stables.
He's one of British racing's leading trainers, having enjoyed top-class success all over the world.
Cumani has twice won racing's most prestigious race - the Derby at Epsom - with Kahyasi victorious in 1988 and High Rise a decade later. Commanche Run had earlier given Cumani a St Leger win, while among other Classic stars to have resided in the yard have been Barathea, Ensconse, Zomaradah and Gossamer.
It's not the first time the trainer has had to contend with fire at the Newmarket stables, there was damage during a blaze in 1997.