Swiss federal prosecutors said they had "concrete indications" pointing towards political espionage, but refused to say who they were targeting.
It came a day after the Swiss foreign minister told his Turkish counterpart Swiss authorities would investigate any illegal intelligence activities.
Turkey is due to hold a controversial referendum next month.
The referendum would give President Recep Tayyip Erdogan sweeping new powers. But in order to get it through, he needs to win the vote of Turks living at home and the more than four million citizens living abroad.
Read more:
But his attempts to hold "Yes" rallies in a number of European countries have been blocked, leading to rows with both Germany and the Netherlands, as well as the wider European Union.
Switzerland, home to more than 70,000 Turkish nationals, has tried to stay neutral. However, local media reported Turks critical of Mr Erdogan's government were being spied on during a lecture at the University of Zurich earlier this month.
More recently, a member of Switzerland's upper house of parliament filed a lawsuit accusing two Turkish organisations of spying on Turkish citizens and dual nationals living in Switzerland, and requested an  investigation.
On Friday, the office of the attorney general said in a statement it "has been made aware of concrete suspicion that political espionage has likely been conducted involving the Turkish community in Switzerland", confirming it had opened the investigation on 16 March.
Swiss prosecutors are investigating claims Turkish citizens living in Switzerland are being spied on.