The agency will be sending out some of its leading lights to Brazil to promote The Open Government Partnership (OGP) conference in April.
Launched in September, the campaign was founded by eight governments including Brazil, Indonesia, Mexico, Norway, Philippines, the United Kingdom and the United States, and mentioned in a joint editorial piece in The Washington Post by Cameron and Obama recently.
The emphasis is on multilateral work to secure concrete commitments from governments to promote transparency and empower citizens.
Havover director Gavin Megaw said: 'It will be a high profile opportunity for us to do something on the world stage and we will be there to provide full strategy and implementation for the conference. It's helping take Hanover forward in terms of our global footprint.'
Agency MD Charles Lewington added: 'Open government has the opportunity to be this generation's big social movement; we look forward to playing our part in communicating how the world is embracing it.'
Lewington will be joined by Megaw in heading to the Brasilia-based conference, which will also engage with businesses, and leading the comms effort from the front.
Meanwhile, the agency will be drawing on its own Portuguese-speaking team to help promote the event, with a social media hub based in London led by Chris Woods.
The OGP conference will include presentations, small group discussions and exhibitions, as well as the formal entry of 42 new countries into the movement.
Caroline Mauldin, an adviser to the US Undersecretary of State for Civilian Security, Democracy, and Human Rights said Hanover could deliver 'real impact' for the conference.
She went on to add: 'Hanover's experience in handling senior political figures at high profile events was very clear.'
The British Prime Minister gave further backing to the OGP project alongside his US counterpart during his official visit to America earlier this month.