It was reported last Saturday the billionaire had acquired shares in the operator, with Tilman Fertitta also said to have become an investor; Icahn made the move public in a filing with the Securities and Exchange Commission on Tuesday.
The investor is far from content with proceedings as they are, however, calling for representation on the Caesars board and urging the company to sell itself.
Caesars CEO Mark Frissora announced he was stepping down in November but is yet to be replaced and Icahn wants the company to delay any future appointment.
Fertitta, meanwhile, sought a "reverse merger" with Golden Nugget in October but saw the offer rejected by the Caesars board.
The operator is still undergoing restructuring following its bankruptcy in 2015.
Uncertainty is fuelling opportunity for investors such as Icahn, though, who was the world's 73rd-richest person in 2018 and has since risen to 63rd, according to Forbes.
Caesars shares are up in 2019, having started the year trading at $6.92 and closing on Tuesday at a share price of $9.62.
