The two leaders were to sign agreements on defence, terrorism and the construction of Britain's Hinkley Point nuclear reactor by France's EDF power company.
They also intend to invest two million euros in developing next-generation military drones.
But they also addressed the migrant crisis in Europe.
Hollande warned of "consequences" for the management of migrants with Britain if the country voted to leave the European Union after meeting Cameron.
"I don't want to scare you but to tell the truth, there will be consequences ... including on the question of people ... the way in which we manage migration issues," he told repoters.
Analysts said that other European countries will demand action from both countries.
"It is quite likely that France and the UK will both come under a certain amount of pressure from all the European leaders to play a bigger role within the migration crisis," Susi Dennison, a senior policy fellow at European Council on Foreign Relations, told RFI.
"Various things are being discussed at leaders' level at the moment ahead of the migration summit next week, including the idea of a kind of a bigger package on resettlements."
The question affects people in refugee camps in Turkey and possibly Lebanon and Jordan.
"This is something which a number of European states, from the Netherlands' presidency and the German leadership as well, are keen to see other EU states play more of a role," Dennison says. "So I think it's possible that more might be asked of UK and France in that context and those questions will be on the agenda too."
There is also Calais.
Britain has already contributed more than 60 million euros and will now provide an extra 20 million around, according to French European Affairs Minister Harlem Désir.
But what people on the ground really hope for is a proper implementation of measures to help reunite families.
"We need to open safe and legal routes from France, from Calais and from Dunkirk, to the UK for families to reunite," Jean Francois Dubost, the head of the Uprooted People Programme for Amnesty International France, told RFI.
This is a shared responsibility, he argues.
"The French are not so good at explaining or trying to implement the different procedures that already exist to help families getting together ... But also the UK have to give a clear message that they are ready now to help people to be reunified and to put an end to this situation where people are just separated by the sea."
The possibility of Brexit is making the French government nervous.
Economy Minister Emmanuel Macron earlier said that the day this relationship unravels, migrants will no longer be in Calais, adding that France would also roll out a "red carpet" to London's bankers if the UK voted to leave the EU.
"The balance of probabilities from the polling now is that the Brexit won't happen," Anand Menon, the director of the UK in a Changing Europe Initiative, told RFI. "If it does happen, it's really hard to see the consequences because it will require renegotiation of the relationship with the EU and no one knows how that would go.
"In terms of Franco-British relations, you could look at this in two ways. You can either say, 'If Britain votes to leave, the French would be tempted to punish us by closing down the Calais camp'. The other way of looking at it is if Britain leaves the EU, the bilateral relationship with France will become even more important to both countries. In fact that would give insentive not to do anything to upset that relationship."
All of this ties in with the migrant crisis as well.
"How the migrant crisis plays out in the next few months in Europe is going to have quite a bearing on the referendum as a whole because this is the very visible face of Europe at the moment in the UK and it is creating a lot of concern," said Susi Dennison.
"It is one of the central questions the politicians, on both the in and out campaign, will have to address, the extent to which we are more able to control our borders inside or outside the EU."