The crowd of 31,555 at the Nou Camp set a new record for a regular Super League game.
t beat the 25,004 who watched Wigan's Good Friday derby in 2005.
Around 4,000 Wigan fans were in the crowd for the historic match, which Catalans won 33-16.
There was confusion during the second-half when Barcelona initially announced to the media a gate of 26,241.
But that figure, Super League say, was incorrect - and the true figure was 31,555.