The couple announced their split on Friday, just two days before the new year - but the company will honour those who placed bets that the pair would be the first to go their separate ways in 2012.
"William Hill can confirm that they will be paying out on Russell Brand and Katy Perry being the first celebrity couple to split in 2012 despite the timing just before the New Year," the bookmaker said.
"Hills made the gesture after almost 90% of bets placed on the market were for the couple to be the first split in 2012. They were so well fancied to split that their initial price of splitting was backed in from 6/5 down to 10/11 in the two days before the split was announced.
"Hills have now reopened the market making Shane Warne and Liz Hurley the 5/2 favourites to split first in 2012, while the joint second favourites are Alex Reid and Chantelle and Jason Orange and Catherine Tate at 4/1."
Other bets for 2012 include 5/1 that Pippa Middleton is named FHM's sexiest woman, 12/1 that Ant and Dec announce their split and 33/1 that the UK wins the Eurovision Song Contest.
Lindsay Lohan is 11/10 favourite to be the first celebrity arrest of 2012, with Pete Doherty at 5/2 and Courtney Love 4/1.
Recent reports have suggested that Perry wanted Brand to be the one to file for divorce to avoid upsetting her religious parents.