Headed by former Paragon editorial director Damian Butt, Imagine is launching before the new Xbox 360 console comes out in this country in November.
The title will face competition from two other publishers set to launch in the sector. Future, which has the contract for the Official Xbox Magazine, will be launching another official title.
Meanwhile, Highbury Communications, owner of Bournemouth-based Paragon, publishes XBM, a magazine founded by Imagine's Butt.
XBM has already published an Xbox 360 supplement and will also launch in the autumn for Microsoft's new console.
360 will be aimed at the more serious gamer, aged 24 to 35, who will make use of the console's multimedia status.
With the average game player now aged 25, according to Imagine, the magazine will try to avoid the teenage feel to some of the computer games magazines.
Butt said: "The luxury feel, intelligent writing and mature focus means we can write about games in an entirely new way and for an audience which is almost completely neglected.
360's readers are affluent, know what they want, and are the biggest source of future growth for the games industry."