Voting on Turkey's proposed constitutional changes for a transition to a presidential system of governance opened on Monday in six European countries.
Turkish nationals living in Germany, Austria, Belgium, France, Switzerland, and Denmark can cast their ballot until April 9.
Of nearly 3 million Turkish people living in Germany, half are eligible to vote. And there has been some fierce campaigning.
"It is really hard to get a percentage for the undecided group. It's not clear whether they will say 'yes' or 'no' and I think the result of the referendum will be decided by this group," said Ayferinci Pekoz, a CHP representative in Berlin.
The political difference between people voting 'yes' and those voting 'no' is similar to that in Turkey, where 55.3 million people are eligible to vote on April 16.
Some planning to vote 'yes' believe Turkey will have a more secure future under President Recep Tayyip Erdogan. But others say increasing presidential powers will undermine democracy.
TRT World's Kilmeny Duchardt reports from Berlin on the expatriate vote.