The two shows will go head-to-head and overlap by 75 minutes on 13 April, when the ITV talent show begins its new series at 7pm.
The BBC is said to be furious with Cowell and ITV after they opted for an earlier slot than last year, and have responded by bringing forward 'The Voice' to start at 6.45pm so they can hook viewers in first.
Last year, the two shows managed to avoid big clashes, only overlapping for short periods.
In the time when they did, 'The Voice' usually came out on top, but viewers for this year's series have so far dipped compared to 2012.
Cowell accused the BBC of playing 'silly games' with the scheduling last year, having previously said he would prefer ITV and the BBC didn't air their big shows at the same time.
"I just hope they don't play these silly games where [the shows] overlap each other. Because that is a ratings game and we've got to be responsible for stopping that," he said.
So much for that.