After talks in Paris with eight other European Social Democratic leaders ahead of an EU summit this week, Hollande said they were supporting Juncker to become president of the bloc's powerful executive body in Brussels.
Hollande met Italy's Prime Minister Matteo Renzi and the leaders of Austria, Belgium, the Czech Republic, Denmark, Malta, Romania and Slovakia.
Moves to hand the post to Juncker -- a long-serving Luxembourg premier and EU insider -- have triggered the most bitter dispute seen in Europe since the height of the euro crisis.
The British leader sees Juncker as a federalist who will not adopt reforms London says are needed in the 28-member bloc.
A similar mini-summit of centre-right EU leaders in Sweden this month saw some strong opposition to Juncker's appointment although German Chancellor Angela Merkel is backing him, along with the European People's Party, the European Parliament's largest grouping.