BMB won the brief without a pitch and will develop a new campaign due to launch this summer.
Gossard, which has been owned by Courtaulds since 2007, has not retained an advertising agency for three years. In February, it hired Initiative to handle media planning and buying.
The appointment reunites Gossard with Trevor Beattie, BMB's founding partner and a former creative director of TBWA. Beattie first worked on Gossard at TBWA, where he wrote campaigns including a 2001 TV ad that saw a woman in mismatched underwear rushed to hospital.
Gossard, which famously produced the Wonderbra until the mid-90s, split with the agency in 2002 over creative differences. It returned two years later before parting company for good in 2005.
Beattie said: "It's an honour to be working with Gossard again. The best creative work comes out of a great agency and client relationship, and we've already had a great time on Gossard. We've got huge plans for the future."
Miranda Frost, the commercial director of Gossard, said: "It is fantastic for the Gossard brand to be reunited with Trevor and his team again. We look forward to producing the next milestone in Gossard's history with Beattie McGuinness Bungay."