Cricket: Champions' Twenty20 is great idea.
New Zealand's wicketkeeper-batsman, who was one of the stars of the inaugural Indian Premier League, believes the expansion of the format was inevitable.
The two finalists of this summer's Twenty20 Cup will join two teams from India, Australia and South Africa in a tournament which will earn a pounds 2.5m jackpot for the winners.
A venue for the event has yet to be finalised, but both the Middle East and India have been suggested, and McCullum enthused: "It sounds like a pretty good idea to me.
"I don't know the ins and outs of it but any sort of tournament that can generate the incomes, profile and fan-base they are doing has to be good for the game.
"As long as they get the best players out there in competition, I'm sure it will be a success."