"Americans don't need Washington to meet our Paris commitments and Americans are not going to let Washington stand in the way of fulfilling it," Bloomberg said.
Macron, who joined other European leaders in criticising Trump's decision and in vowing to defend the Cop21 deal, described the Paris accord as "irreversible" and hailed Bloomberg as "a key player in the climate battle".
On Thursday Bloomberg said he was launching a coalition of mayors, governors, and business leaders from both political parties to sign a statement of support to reach the emission reduction goals the US made in Paris in 2015.
Bloomberg also pledged to raise 15 million dollars (13 million euros) for the UN's climate body, to make up for US funding likely to be axed by Trump.
The money will support the operations of the Bonn-based secretariat of the UN Framework Convention on Climate Change.
Bloomberg is also president of the C40 Cities Climate Leadership Group, a coalition of 90 cities around the world that is pushing programmes to reduce carbon emissions and shore up urban defences against climate change.
The chair of the group is Paris Mayor Anne Hidalgo, who was also present at Friday's talks.
French ministry's reply to Donald Trump
In an unusual move on Friday, France's foreign affairs ministry issues a fact-check of Donald Trump's claims about the Paris agreement.
Under the terms of the agreement, the US cannot complete its withdrawal until just weeks after the US presidential election in 2020.