The deal with Bodog was initially for two-years but included an option to end the deal after 12 months.
The deal with Zoopla.co.uk, an online property brand begins on June 1 and will run at least until the 2014/2015 season.
The move marks Zoopla's first major foray into sport sponsorship.
The deal means that the Zoopla brand will appear on the West Brom shirts of the players, along with branding at its home ground, the Hawthorns, on official club merchandise and across the club’s website.
The partnership will also offer Zoopla.co.uk hospitality opportunities, player appearances and use of the stadium facilities.
In this year's Premiership season, West Brom finished 10th in the table.
Alex Chesterman, founder and chief executive of Zoopla, said: "The deal will help raise our brand awareness and reach a huge audience and is further step in our mission to make Zoopla a household name, synonymous with online property search and research."
There have been reports of financial problems at Bodog in the US.