The charity has appointed The Fish Can Sing (TFCS) after a competitive pitch to handle a major youth-oriented global PR campaign that will include musicians reworking tracks by the late former Beatle.
The music-based campaign, which will also involve the appointment of an ad agency, is expected to kick off in October across at least eight countries, including the UK and US.
Lennon's widow Yoko Ono gave Amnesty the right to use Lennon's 1971 song Imagine for free for a global promotional push in 2003.
The campaign being planned by TFCS will involve more than Lennon-inspired campaigning, but details currently remain under wraps.
A TFCS team based out of London and its recently opened New York office will work on the campaign.
Rogers & Cowan, Edelman/Jackie Cooper PR and Publicis are believed to be other agencies that were in the running for the contract.