The agreement will make MGM Resorts the 100% owner of CityCenter on the Las Vegas Strip, a complex made up of Aria Resort & Casino and Vdara Hotel and Spa.
Shares of the Las Vegas company were up 2.32% to $43.62 on Thursday.
The purchase price for CityCenter represents an implied valuation of $5.8 billion based on net debt of $1.5 billion.
After the transaction, MGM said it will sell the Aria and Vdara properties to private equity firm Blackstone for $3.89 billion in cash.
Blackstone will lease both the properties to MGM for an initial annual rent of $215 million, the company said.
The transactions are expected to close in the third quarter. The closing of the Infinity World transaction is not contingent on the closing of the transaction with Blackstone, MGM said.
"Uniting all of CityCenter under MGM Resorts' corporate structure and strategy will allow us to consolidate financial results, build on efforts to strengthen our operating model and guest experience and further our vision of becoming the world's premier gaming entertainment company," Bill Hornbuckle, CEO and President of MGM Resorts, said in statement.
In May, J.P. Morgan upgraded MGM to overweight from neutral, saying "momentum at its domestic casinos, particularly in Las Vegas," continues to "build revenues and margin improvement."
In that same month, Nevada officials approved 100% occupancy with no social-distancing requirements on the gambling floors in the company's nine Las Vegas properties.