The agency won the business after a competitive pitch that kicked off last month, handled by the Barclays procurement department.
Barclays previously used a roster of agencies across its DM activity, including Balloon Dog, Soho Square, Teamspirit and VCCP me. In September 2010, Havas EHS landed Barclays' consumer-facing DM business.
Rapp, which previously worked on the Barclaycard chunk of the business, will now oversee the company's entire DM account.
Barclays' global digital review, which is being run separately, is still ongoing. The brief covers digital advertising across Barclays' entire business.
Barclays spends more than £11 million on direct mail and digital, according to Nielsen.
Bartle Bogle Hegarty and Maxus, which handle advertising and media respectively, are unaffected.Follow @SaraKimberley