Polling stations in Sydney, Canberra and Melbourne, Australia, will be opened at 9 pm Croatian time on Saturday.
After Australia, polling stations will be opened in Japan and China.
The last polling station to open will be in Los Angeles at 4 pm Croatian time on Sunday.
Fifty countries have consented to holding Croatia's presidential run-off, which sees incumbent President Stjepan Mesic facing the candidate of the ruling Croatian Democratic Union, Jadranka Kosor, for the next five-year term.
About 400,000 Croatians residing abroad are eligible to vote at 155 polling stations, the most of which are in Bosnia-Herzegovina (42), Australia and Germany (15 each), and Serbia and Montenegro (seven).