Brett, who departs in September, will oversee consumer work at Ogilvy offshoot Pulse Communications.
He fills one of four group MD roles created as part of a wider restructure within Ogilvy's Australian set-up.
Brett said: 'It was a lifestyle choice. I wanted to live abroad and this is an opportunity to make that happen. I am looking forward to broadening my global experience and working at a major global network.'
Brett has been at Shine for four years, and was previously global vice-president, marketing comms, at Samsonite.