"Nigeria and Cameroon need to have the best possible relations, to work together," Hollande said, adding that that was the "spirit" of a previous conference in Paris in 2014.
Cameroon, Chad and Niger have joined Nigeria in military collaboration to fight Boko Haram, which has stepped up attacks against neighbouring countries from north-east Nigeria.
Hollande called for international aid to help deal with the tens of thousands of Nigerians who have fled their country because of the armed Islamists' violent campaign and promised more aid from France.
Having praised Benin's President Thomas Boni Yayi for promising not to stand again at the end of his term next year, Hollande declared that both security and democracy were necessary for development after meeting Biya, who has been in power for 32 years.
"We are mindful of all possible efforts to allow pluralism to have its rightful place," he said. "We are also mindful of freedom of expression and respect for human rights."
"You don't stay in power because you want to but because you can," Biya commented when asked about the length of his presidency. "I didn't come to power in a dictatorial way, I have always been elected by the people."
Hollande's comments during his two-day tour of three countries earned criticism from the Democratic Republic of Congo, a former Belgian colony.
"There's no need to lecture us," said government spokesperson Lambert Mende. "We aren't democratising African countries to please M Hollande, the French government or I don't know what French public opinion. We aren't going to put up with this sort of paternalism 55 years after independence."
In Cameroon Hollande admitted that there had been "tragic" episodes during the country's fight for independence from France in the 1950s.
"We are open to the history books being opened and the archives, too," he said.