Bloom's stake will be in non-voting shares, and he has nominated James Franks, a long-time business consultant with experience in football governance, to join the club's board as a non-executive director.
"I firmly believe in the club's ability to disrupt the pattern of domination of Scottish football which has been in place for far too long," Bloom said in a statement.
"The appointment of James as my representative on the board underlines the importance I attach to my investment in the club.
"James has been a trusted associate of mine for many years, and I believe that his wealth of experience in the football industry and strong business acumen will be a tremendous asset to the board and to the club."
Hearts finished seventh in the Premiership last season, reached the Scottish Cup semi-finals and played in the league phase of the Conference League.
Bloom is also an investor in Belgian Pro League team Royale Union Saint-Gilloise, who ended their 90-year wait for the league title in the 2024/25 season.
In March, he also reached an agreement to acquire an initial 19.1% stake in Australian A-League side Melbourne Victory.