The purchase has raised his stake from just under 10% to 15.6%; the announcement follows news Icahn has secured board positions at Caesars for Icahn Group executives.
Keith Cozza, CEO of Icahn Enterprises, and Courtney Mather and James Nelson, both Directors at the same firm, all recently joined.
At the time of these appointments, Icahn re-emphasised his belief a strategy based on M & A would best suit Caesars.
He said: "I believe the best path forward for Caesars requires a thorough strategic process to sell or merge the company to further develop its already-strong regional presence, which will allow Caesars to continue to take advantage of the Caesars Rewards program bringing more and more players into Caesars' Vegas market."
Caesars is still looking for a new CEO, with current CEO and President, Mark Frissora, due to leave the operator in April.
Reports suggest Icahn is keen to hand the role to Affinity Gaming CEO, Anthony Rodio, who worked for Icahn as CEO of Tropicana Entertainment. Icahn bought Tropicana in 2008 when it faced bankruptcy and sold it last year for $1.85bn.
If a CEO is not appointed within 45 days, Icahn will be allowed to add another member of his choosing to Caesars' board.
