Following the appointment, The7stars will plan and buy UK campaign for the Galacasino.com and Galabingo.com brands. It will also work on media for the Swedish site Gala.se.
The7stars beat Home, the incumbent, to the business.
The7stars already works with Gala Interactive’s sister company Coral Interactive. The Coral and Gala accounts will be run through separate teams.
Phil Walker, the chief marketing officer at Gala Interactive, said: "We look forward to working closely with The7stars to drive our business into its next exciting growth phase. The7stars has performed strongly for our sister company Coral Interactive for many years and we expect similar success with Gala Interactive."
Gala Coral Group is a betting, bingo and casino company formed in 2011 operating 1,800 betting shops. In addition to its newly launched Swedish site it also has 780 Eurobet shops in Italy.
Liam Mullins, the head of trading at the7stars, said: "Following a fantastic relationship with Gala Coral Group we are looking forward to working with Gala Interactive and its defining online brands.
"GalaCasino and GalaBingo are at the forefront of the UK’s gaming proposition and we’re excited to help grow these brands even further."
Gala Interactive spent £5.7 million on media in 2013, according to Nielsen.