"If the operation became more than fighting a potential terrorist threat on the Turkish border and turns out to be an invasion operation, we would have a real problem with that," Macron told Le Figaro daily.
The US and France have repeatedly expressed concern over Turkey's 12-day cross-border offensive against the Kurdish People's Protection Units (YPG), which Turkish President Recep Tayyip Erdogan last week threatened to expand.
Ankara views the YPG as a terror organisation allied to the outlawed Kurdistan Workers' Party (PKK) inside Turkey but the US has been backing it as an ally in the fight against the Islamic State group.
On Tuesday, Foreign Minister Jean-Yves Le Drian said that if the operation turned into an "occupation" of parts of Syria, it would be "totally reprehensible".
His remarks came after Erdogan threatened to push further east along the Syrian-Turkish border, until there was "no terrorist on our border leading to Iraq".
He also vowed to "clean up" the YPG-held city of Manbij east of Afrin, where the US has troops.
Macron said Turkey's operation required Europe and its allies to "have discussions and take decisions", without specifying what they might be.
