The Halo maps will arrive on the console in spring next year as part of the Xbox Live service.
"We're not setting out to change the industry," said Certain Affinity founder Max Hoberman. "We're creating games by choosing strong leaders, talented and experienced developers, and solid partners. This partnership with Bungie and Microsoft Game Studios is a piece of that puzzle and we hope it's the start of a long and fruitful relationship."
Former Bungie man Hoberman worked on both Halo 2 and Halo 3 as a multiplayer leader before leaving to set up Certain Affinity.
He has picked his staff from former employees of developers such as Origin, Digital Anvil and Bungie. Members of his team have previously worked on titles including Ultima, Wing Commander, Myth and the Ghost Recon series.
Halo 2 was until recently the most played game on Xbox Live, but was overtaken by another first party title last month – Epic’s Gears Of War.
Halo 3 is scheduled for release on 360 in spring 2007. Microsoft and Bungie have teased fans by announcing a free-to-play multiplayer Beta, which will be available for gamers at some stage early next year. Registrations have already begun in the US, while European gamers are still being made to wait.