Consolidated will promote the Queen's Award for Voluntary Service, having been appointed by the Office of the Third Sector, based in the Cabinet Office.
Consolidated took part in a three-way pitch managed by the Central Office of Information.
The award recognises excellence in volunteering in local communities throughout the UK, the Channel Islands and the Isle of Man.
The brief is believed to be worth six figures and Consolidated's main objective is to increase the number of nominations by driving awareness of the awards.
Board director Anthony Moore, who leads the agency team, said: 'We are going to try to get out to hard-to-reach audiences. In particular, we will be looking at BME audiences, who are under-represented in winning the awards. That's where the ambassadors come in, as well as BME-related media.
'It's going to be a challenge to keep up the momentum, as there's a rolling process of nominations over several months.'
Activities will focus on local communities through a regional events programme around the country.
Consolidated will also use high-profile people who take part in volunteering as 'awards ambassadors' to get case studies into the local and national press. The agency will handle the announcement of the winners by the Queen from Buckingham Palace on 2 June and work closely with the palace's press office in the run-up to the announcement.
Consolidated has secured the account for three years. It was previously held by Geronimo Communications.