The former US president said in a 70-second message: "The French election is very important to the future of France and the values that we care so much about.
"[Mr Macron] has stood up for liberal values. He put forward a vision for the important role that France plays in Europe and around the world.
"He appeals to people's hopes, and not their fears. I know that you face many challenges and I want all of my friends in France to know how much I am rooting for your success."
In the final TV debate before Sunday's second-round ballot, Mr Macron labelled his opponent, the National Front's Marine Le Pen, the "high priestess of fear".
In turn she called him a "darling of the system" and said he was "complacent" on extremism.
Mr Macron has accused the far-right Ms Le Pen of spreading lies by suggesting he had an undisclosed offshore fund.
His party said it was taking legal action after an internet campaign suggested shortly before the debate on Wednesday night that he had concealed funds in a foreign tax haven. Mr Macron himself denied the allegation.