According to sources, Maxus has won a pitch against the incumbent, Walker Media, which pitched alongside Havas Media, and OMD.
Barclays, which approached media networks with a pitch brief in July, spends £31 million on UK media for its main brand and Barclaycard, according to Nielsen Media Research. It also operates in around 50 other countries and, during the pitch process, held meetings with agencies in various locations around the globe.
Walker Media, which is part of the M&C Saatchi Group, had worked on the account since 2006.
The review of the Barclay's media planning and buying business is understood to have been called by the chief executive of the Barclay's Group, Bob Diamond.