It is understood that BMB will develop a new campaign to coincide with increased investment into the brand.
Work is expected to include radio, print and digital media.
The incumbent, Hooper Galton, which has worked on the account since 2005, withdrew from the process
Globally, Nando's is known for its humorous, yet controversial, ad campaigns.
One ad that aired in South Africa in 2000 featured a blind woman being led into a pole by her guide dog, which then ate the chicken that the woman had just bought.
Last September, Nando's hired Love, the Manchester-based creative agency, to develop a campaign for its retail range of branded sauces, marinades and dips after a three-way pitch. Love's relationship with Nando's is unaffected by BMB's appointment.
A spokesman for Nando's said that a final decision had not yet been made. BMB declined to comment.