Rank Group, the owner of Mecca Bingo, has bought 23 casinos from Gala Coral.
The deal will make Rank the biggest operator of casinos in the UK, as it already owns Grosvenor Casinos which operates 35 clubs.
As well as the existing casinos, Rank is also buying licences to operate three more. Rank is controlled by Malaysia's Guoco Group.
Gala Coral will keep casinos in Dundee, Gibraltar and the licence for a club in central London.
Rank attempted to buy the casinos earlier this year, but talks broke down at the end of March.
In a statement Carl Leaver, chief executive of Gala Coral, said: "Under Rank's ownership I am sure that the business will continue to go from strength to strength."
"This transaction will crystallise significant value for our shareholders and debt investors."
Gala Coral has been controlled by private equity firms since its debts were reorganised in 2010.
The deal still requires approval from shareholders and competition regulators.