The star is among several new investors in the parent company of Team Liquid – a powerhouse of esports across multiple titles, including League of Legends.
It follows a trend of significant fundraising by north American League of Legends Championship Series franchises this year.
Co-chairman of aXiomatic Ted Leonsis commented: "The next generation of sports fans are esports fans.
"Esports is the fastest-growing sector in sports and entertainment, and aXiomatic is at the forefront of that growth. We are thrilled to welcome Michael to aXiomatic and look forward to working together on some truly cutting-edge opportunities."