France's defence ministry disputed the finding, saying the 3 January strike targeted an "armed terrorist group".
France has 5,100 troops across the Sahel region to fight militants tied to al-Qaeda and the Islamic State group.
The UN carried out an investigation after locals alleged that a helicopter had fired on people attending a wedding near Bounti village in central Mali.
The investigation found that a wedding had taken place, and there had been "about 100 civilians at the site of the strike", AFP news agency quoted the UN report as saying.
