Brady and Clijsters are part of a group led by Knighthead Capital Management.
The MLP will expand from 12 teams to 16 next season, with the number of events doubling from three to six and the total prize money set to surpass $2million.
"Of course, I'm excited at the investment opportunity," Belgian Clijsters, who won four singles Grand Slam titles, said on Wednesday.
"But what excites me the most about becoming an MLP owner is that I get to help shape the future of pickleball, a sport I have come to love... I'm thrilled to help showcase professional pickleball and make an impact on the sport."
Invented in 1965, pickleball is a fast-paced paddle sport similar to tennis and badminton, though it is played on a smaller court with a net using a perforated plastic ball.
A Sports and Fitness Industry Association report released in February said it was the fastest-growing sport in the United States with more than 4.8 million participants in the country and growth of almost 40% in the last two years.
