Insurance group Friends Life has elected to end its four-year sponsorship once the 2013 season is finished.
Freuds has been charged with spreading the word about the tournament following a competitive pitch.
The agency appointment also follows an ECB review of the county cricket schedule, with changes planned for 2014 including playing Twenty20 league games mostly on Friday nights.
Comms work will include developing the 'Something Completely Different' campaign promise from 2012.
Central to the ECB's positioning will be the message that the tournament is a unique sporting experience, with a focus on its fast pace and accessibility.
ECB head of marketing Will Collinson said: 'Freud Communications' proven pedigree will help us develop the brand promise of t20 cricket - "Something Completely Different" - and continue to raise the profile of this unique competition.'
Alluding to a cricketing programme that includes the Ashes series, a spokesperson for Freuds added: 'Cricket will be at the forefront of the sporting agenda next summer and we will look to capitalise upon that.'
PRWeek revealed last year that the work, previously handled by incumbent Frank PR, was up for grabs alongside profile-raising for other events including the Investec Series against New Zealand.
It is understood Frank did not repitch and that the organisation is still in talks over other aspects of its agenda.
The domestic Twenty20 tournament was launched in 2003, and will run from June to August this year.