Inbox will set up in the offices of digital agency, Hyperlaunch. Both agencies are owned by AIM-listed marketing services group Digital Marketing Group.
A team of 12 spanning across account management, creative and technical will staff the new office. Some existing Inbox staff from its Swindon office will move to the Bristol office. New joiners include account director, Greg Richardson, who joins from direct marketing outfit DMS.
The expansion is being steered by Matt Ramsay, the agency's chief executive, who was recently promoted from business development director.
Ramsay said: "This is a pivotal moment for Inbox. With the business flourishing, now is the right time to start further building our presence geographically so we can offer all the benefits of a buzzing city with easy access to the rest of the UK and Europe."