The merger is expected to create Europe's biggest privately owned gaming company, with a combined marketing spend of £10m. The enlarged business covers betting shops, bingo halls, casinos and online activity.
A Gala spokesman said there would be no job cuts following the merger, but it was too early to comment on the business' structure. It is not known what role Coral Eurobet marketing director Nick Mills will have.
Gala is likely to look for an advertising agency to service the combined company. Last year Gala spent nearly £3.3m on advertising, while Coral spent about £2m, according to Nielsen Media Research.
Gala's current direct agency is Tequila\London; Coral works with PHD Compass on its direct marketing and press ads.
The spokesman said it was too early to discuss future supplier arrangements.