The gambling and racing company announced the transaction to buy the Riverwalk Casino and Hotel in Vicksburg earlier this month.
Riverwalk opened in 2008 and is operated by Magnolia Hill and owned by High River Gaming, JB3 Corp. and Taiman Holdings Corp.
Churchill Downs said Tuesday that the acquisition received approval from the Mississippi Gaming Commission.
Shares of Churchill Downs shed 74 cents to $61.54 in afternoon trading amid a broad market decline. Its shares have traded between $42.14 and $65.34 over the past year.