Adidas sources have dismissed reports that the new agreement is worth 120 million euros a year to Real Madrid.
Adidas will extend its sponsorship of LaLiga club Real Madrid until 2028, it was announced on Wednesday, as the German sportswear firm battles fierce competition in Europe from Nike and a resurgent Puma.
Adidas has seen its leadership in football eroded in recent years by the advance of its bigger US competitor Nike, which sponsors Real's arch rivals Barcelona and is reportedly in talks with Liverpool, second in the English Premier League.
"This agreement will help us to achieve our mission to be the best sports company in the world. It also underpins Adidas' leadership in the football category," the firm's chief executive, Kasper Rorsted, said in a statement.
Real Madrid chief: "Adidas is an ideal sponsor for us"
Real club president Florentino Pérez said: "It is a natural step to extend our successful deal until 2028. Together we will continue to build this strategic alliance that helps us set a benchmark and remain leaders in football. Adidas is an ideal sponsor for us."
No financial details were given of Adidas' new agreement with Real, who are third in LaLiga and made an early exit from the Champions League.
Fierce competition among Adidas, Nike and Puma for the top clubs in Europe has driven record deals in recent years, but company sources dismissed as much too high a figure of 120 million euros a year cited by some media.
Adidas last week reported that sales fell 3 percent in Europe in the first quarter, but said it hopes for a recovery by the end of the year as it seeks to boost sales of sports performance gear.