The Greek coastguard said that one of its patrol vessels was "harassed" by a Turkish patrol boat on Sunday, causing minor damage, a day before the Greek and Turkish leaders hold talks in Brussels.
There were no injuries in the incident, which occurred east of the Aegean island of Lesbos, the coastguard said in a statement.
It said "a patrol vessel of the Turkish coastguard harassed a patrol boat of the Lesbos coastguard, causing minor damage".
Such incidents are common in the Aegean Sea during patrols for boats carrying migrants from Turkey to Greece.
Greece in April had accused Turkey of seeking to "provoke an escalation" in the Aegean with "dangerous" manoeuvres and illegal assistance to migrants.
Athens wants Ankara to better police migration routes and take back hundreds of asylum seekers found ineligible for refugee protection.
Prime Minister Kyriakos Mitsotakis is to hold talks with Turkish President Recep Tayyip Erdogan on Monday on the sidelines of a NATO summit in Brussels.
Mitsotakis said on Friday that good bilateral relations will depend on de-escalation efforts and on whether "Turkey participates constructively in the dialogue and respects the conditions set by the EU" in accordance with international law, including the UN Convention on the Law of the Sea.