The Premier League side, currently 15th in the table and four points above the relegation zone, have been partnered by the sports manufacturers since 2011 and will continue to do so for the next two seasons.
Adidas, who provide the club with all playing and training gear and also act as technical partners, will now remain with the club until at least 2016.
Albion's chief executive Mark Jenkins told the club's website: "We have enjoyed an extremely successful partnership with adidas over the past three years and are looking forward to working with such a leading worldwide brand for a further two seasons.
"Adidas is renowned for the design and quality of its sportswear and this has culminated in a club-record turnover in our retail stores this season.
"We are now looking forward to unveiling our new adidas home and away kits and training gear in the coming weeks."
It is also believed the Baggies plan to introduce a pinstriped shirt for the 2014/15 season, opting to differ from the traditional blue and white stripes design that has been in place since the Second World War.