The agency, which pitched against three undisclosed agencies, will now be responsible for a marketing campaign to raise awareness of Brook's sexual health services among its target audience of under-25-year-olds.
The pitch process, rather than being led by Brook's senior marketing team, was determined by a group of Brook teenage volunteers. The group, guided by senior marketers, were responsible for writing the creative brief and had the final decision on which agency won the account.
Baber Smith's campaign, which will incorporate press, outdoors, online, PR and selected retail partnerships, will launch in June.
Jules Hillier, director of communications at Brook said: "It's important that our marketing resonates strongly with our under-25 audience, so what better way of ensuring this than by entrusting our fantastic volunteers to handle the pitch process?"
Brook provides free and confidential sexual health advice and support, and aims to help young people make informed decisions about their personal and sexual relationships.