The premiers were joined by their interior and justice ministers, along with representatives of the military, police and intelligence services of both countries, and the magistrates leading the Paris attacks investigation.
"The main message is that we stand side by side and are determined to work to increase the level of security for our citizens," Michel told a joint press conference after the two leaders met in Brussels.
"We must be united around our values, cooperate and become stronger against terrorism. I have never doubted the Belgian people," Valls added.
Belgium's police and intelligence services were criticised after it emerged that some of the Paris attackers and alleged accomplices came from the Brussels neighbourhood of Molenbeek.
Since mid-November 11 people have been arrested and charged in Belgium in connection with the massacre. ey suspect Salah Abdeslam and his friend Mohamed Abrini, who are both from Molenbeek, are still at large.
The Islamic State armed group said four of the nine assailants were of Belgian origin, including one of the organisers, Abdelhamid Abaaoud, who was killed in a French police raid days after the massacre. Three others were French and two were Iraqi.
On the wider EU front Valls called during for a "European security pact," which he said was vital if Europe's passport-free Schengen area is to survive the migration crisis.
"Schengen musn't be, cannot be only a space for free movement, but also a space for security. The future of this concept is today under threat."
He stressed the importance of sealing a deal to track and share airline passenger names as part of efforts to prevent a repeat of the Paris attacks, some of whose perpetrators travelled freely across Europe before the carnage.
Both governments also backed plans by the European Commission to modify Schengen rules in order to "restore external border controls in a systematic and obligatory manner," including for EU passport holders.
Faced with terrorism, which Valls described as "a war that would continue", pointed out that France was seeking with cooperation with other EU member states when it came to police cooperation and intelligence.
"The Schengen Intelligence System (SIS) must be systematically updated so that all people who pose a terror threat are clearly labelled as such," he said.
The countries have also agreed to work more closely with the European parliament and other partners to quickly finalise a deal on gun control.