OMD will take over from Mediaedge:cia, which had been the incumbent on the consolidated business since September 2007.
OMD's appointment is the first major account move made by Monster since Ted Gilvar joined the company as its new chief global marketing officer last year.
In recent years, Monster has spent around $200 million per year on its global marketing work.
Creative is currently handled by BBDO, which recently rolled out a campaign for the brand called "Are you in the right job?" to tie in with the climax to the NFL season.