The business was previously held by Initiative Media Worldwide and moves to OMD following discussions that also involved MindShare and Carat.
However, it is understood that no formal pitch took place and the account was won following OMD Europe's discussions with Allianz in Germany.
The appointment of OMD does not affect John Ayling & Associates, which handles the UK business for the Allianz-owned Cornhill Insurance. Allianz will also continue to use other agencies for local activity.
OMD's appointment on the global corporate account, which involves building the Allianz brand across international TV and print titles, follows its success in winning the Allianz media account in Asia, worth around $10 million, a year ago.
Its sister agency BBDO Worldwide creates Allianz's corporate advertising but lost the creative account in Germany to Bates Worldwide last October.
Initiative was appointed by Allianz four years ago and planned and bought campaigns that ran across 27 countries. It had won the account following a pitch against the BBDO-owned agency GFMO Hamburg.
The bulk of the budget for Initiative's campaigns was focused on Europe, with Asia and South America also targeted.