The retailer, which specialises in luxury cashmere clothing, said the agency would be creating a new logo and brand identity for the N.Peal and devising an in-store promotional activity campaign.
N.Peal said it wanted the rebranding to focus on the quality of the Mongolian cashmere it produces and the brand's heritage as a family-run business.
The work, which is set to be unveiled in the autumn, will coincide with the relaunch of the brand's flagship store in London's Burlington Arcade.
Ashley Bolser, director of ABA, said: "Winning the N.Peal rebrand project has been incredibly exciting for us and it has been a real challenge to take an established brand with a heritage such as this, and give it relevance today.
"N.Peal have many untapped qualities to their products, which we hope to reveal and promote with their rebranded image."
The agency's clients include , Debenhams and Norwich Union.