Mr Root will help to raise the brand visibility of Brewin Dolphin, which has an office in Leeds.
The wealth manager’s logo will be displayed on one side of his bat during all his matches.
A Brewin Dolphin spokesman said: "Joe will also engage in various virtual and in-person appearances, a cricket clinic, social media activity, content creation and will also provide signed merchandise that will be auctioned off for charity."
Mr Root said: "With supporters having been denied competitive sport for so long, it is great to see them return and fantastic to join forces with such a prestigious company as Brewin Dolphin. I look forward to activating an exciting and engaging partnership with them."
Michael Craven, head of office for Leeds at Brewin Dolphin, added: “With Joe scoring centuries in the first two Tests of this summer, including the magnificent 180 not out at Lords, we eagerly await the third Test at Joe’s home ground of Headingley to see if this great form continues.”
Root was part of the England squad that won the 2019 Cricket World Cup and was England’s leading run-scorer in the tournament.
He scored his first Test hundred at Headingley in May 2013. He was crowned Wisden Cricketer of the year the following year.
A two-time Ashes winner, Mr Root reached the top of the world batting rankings in 2015 and was appointed Test captain at the start of 2017.