The retail specialist won the pitch that began in November last year and was handled through the intermediary Creativebrief.
It will work alongside Birds Eye's ad agency, Abbott Mead Vickers BBDO, and its media agency, Carat.
The agency's initial focus will be on targeting Birds Eye's key audiences, with the aim of changing consumer perception of frozen foods. It will also work across shopper marketing, promotional and experiential activity.
Live & Breathe will be Birds Eye's first retained DM agency. In the past, the brand has worked with a number of agencies on an ad hoc basis.
Angus Peterson, the head of marketing at Birds Eye, said: "Live & Breathe demonstrated an appreciation of the FMCG space. It also possesses the gravitas and strategic credentials that we require of an agency taking on this role."