Brazen won the account, which was previously held by Mercieca, through a three-way pitch.
It will be responsible for traditional and digital media and will work on a disruptive PR campaign to reinforce and build on the reputation of Pilgrims Choice, which is the second best-selling cheese in the UK after Dairy Crest's Cathedral City cheddar.
It will also work on introducing new mature cheddar cheese brand Mu, which is aimed at mothers and children.
Brazen will report to Adams Foods director of brands Mike Harper and the account will be led by Brazen MD Gary Bramwell.
Brazen founder Nina Webb said: "Pilgrims Choice is already an established hero brand in the cheese market but we want to really push the boundaries with its public relations.
"The brand has an enviable approach to its marketing and comms and we will reinforce and extend its reach with a portfolio of fresh and exciting campaign ideas. We’re delighted to be working with one of the most forward-thinking brands out there."