Caesars Entertainment said the Showboat is the poorest-performing of its four casinos in Atlantic City.
"While we regret the impact that this decision will have on our Showboat associates, we believe this is a necessary step to help stabilize our business in Atlantic City and support the viability of our remaining operations in the vicinity," said Gary Loveman, chairman and chief executive officer of Caesars Entertainment.
The Showboat opened its doors on March 30, 1987. Caesars Entertainment acquired it 11 years later by purchasing Showboat Inc. The property has 1,331 hotel rooms and employs more than 2,100 people.
The Showboat had a gross operating profit of nearly $2 million in the first quarter of 2014, down from nearly $8.5 million a year earlier, according to The Associated Press.
Loveman, Caesars' CEO, said earlier this year that Atlantic City has too many casinos and that more need to close.
The Showboat will be the second casino to close this year in the nation's third-largest gambling market. The Atlantic Club closed in January.
Revel Casino Hotel, the newest and northernmost casino on the Atlantic City boardwalk, has warned it might shut down if a buyer can't be found in bankruptcy court.
In addition to the Showboat, Caesars also owns the Caesars, Bally's and Harrah's casinos and hotels in Atlantic City and the Harrah's casino in Chester, Pennsylvania.