Russian chief of staff Valery Gerasimov "discussed on the phone the coordination of troops" in operations against IS in Syria with his French counterpart Pierre de Villiers for an hour, the Russian defence ministry announced on Thursday.
Earlier Russian Foreign Affairs Minister Laurent Fabius told France Inter radio "We think they are sincere and we must bring together all our forces" and Russia's Sergei Lavrov said Moscow could work with the US-led anti-IS coalition as long as it respects Syria's sovereignty.
President François Hollande's called this week for the "bringing together of all those who can realistically fight against this terrorist army in a single, broad coalition".
And Russian President Vladimir Putin ordered his navy to the Mediterranean to work with the French as "allies".
That's a big change in both countries' attitudes.
France has refused to deliver two Mistral warships to Moscow and joined European Union sanctions on Russia because of the Ukraine conflict.
But the two countries have found a common enemy in IS, with Putin finally publicly acknowleding that the group was behind last month's downing of a Russian passenger jet over Egypt and Hollande declaring that France is "at war" with the armed Islamists.
Up until now Paris has objected to Moscow's alliance with Syrian President Bashar al-Assad, insisting that he has to be toppled, but that stance seems to be softening.
Hollande is to go to Moscow on 26 November to meet Putin after seeing US President Barack Obama in Washington two days beforehand.
On Wednesday Russia submitted a revised draft UN resolution on fighting IS and France said that it could be partly included in its proposal to the Security Council.