"We must do everything so that (the democratic process) can remain the basis of pluralism" in Egypt, Hollande told reporters at a joint news conference with Tunisian President Moncef Marzouki.
"It is a failure when a democratically elected president is deposed," he said referring to the Egyptian army's ouster of Islamist president Mohamed Morsi on Wednesday after massive nationwide protests.
Tunisia is ruled by the Islamist party Ennahda which is close to Morsi's Muslim Brotherhood, and has faced several major challenges to its own political stability in recent months.
"That said, we must understand this signal (from Egypt), pay attention, realise that there are serious economic and social demands" to respond to, said Marzouki.
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Despite a wave of violence linked to radical Islamists, and political tensions notably over the draft constitution, Tunisia is considered the Arab Spring country most likely to succeed in making its democratic transition.
With its historical ties and investments, France has a direct interest in seeing it do so.
"What is clear is that for you there is also an obligation to succeed because you are an example, a reference for many other Arabs," the French president said, while describing the political transition in Tunisia as "controlled."
After his talks with Marzouki, Hollande was due to meet Prime Minister Ali Larayedh, who belongs to Ennahda, and will address the National Assembly on Friday.