The San Francisco-based startup did the same last month with Houston Texans running back Arian Foster.
Fantex CEO Buck French told ESPN.com that it paid Davis $4 million to the rights to 10 percent of his future earnings, which includes his playing contract, endorsements and income after he retires from professional football.
The company said it will create stock that allows the general public to invest in Davis.
In 2010, the tight end signed a five-year deal with the 49ers in which $23 million is guaranteed. His base salary this season is $6 million.
Davis, who is in his eighth NFL season, has 518 receiving yards with seven touchdowns this year.
His endorsements include Force Factor sports supplements and Krave beef jerky.
French said the company will start taking reservations next week on its interest in Foster, to whom the company paid $10 million for a 20 percent share of his future earnings.
The deal was approved by the Securities and Exchange Commission. French said the goal is to begin trading Foster stock by the end of November.