RKCR/Y&R, which was appointed without a pitch, will work on an integrated campaign that will break in the autumn.
The incumbent is Leith, which won the business in 2011. It was previously handled by J Walter Thompson and, before that, The Union.
Baxters is a Scottish-based company that also produces chutneys and preserves.
Jaspal Chada, its global marketing director, said: "Baxters is a much-loved British brand with a rich heritage, but it also needs to continually evolve.
"We were impressed by RKCR/Y&R’s fresh take on our brand and look forward to partnering with the team there."