The agency, which won the business without a pitch, will develop a campaign to break later this year that is expected to include TV, press, outdoor and online work.
DDB is the incumbent agency on Bovril, although the account has been dormant for some time.
The appointment strengthens Krow's relationship with Unilever. It joined the FMCG group's roster after winning the Elmlea account in 2006.
Unilever is looking to rejuvenate the Bovril brand, which has suffered mixed fortunes over the past few years. In 2004, Bovril removed the beef extract from the product in the wake of the BSE crisis that saw exports drop from 20 per cent to just 7 per cent of its total sales. Beef was reinstated in 2006.
Barry Cook, a founding partner of Krow, said: "Bovril has warmed us all up on the terraces somewhere in the country. To get to work on this iconic British brand is not only a fantastic opportunity, it's also a real pleasure."