Defence Minister Jean-Yves Le Drian said troops would be in place from Tuesday evening in sensitive areas.
It is the first time troops have been deployed within France on such a scale.
Seventeen people were killed in Paris last week in attacks at satirical magazine Charlie Hebdo, on a police officer, and at a kosher supermarket.
On Sunday, an estimated 3.7 million people took to the streets to show solidarity with the victims, including 1.5 million people in Paris.
About 40 world leaders joined the start of the Paris march, linking arms in an act of solidarity.
President Francois Hollande ordered the deployment of troops during a crisis meeting with top officials early on Monday.
Mr Le Drian said the deployment, the first of its kind, was needed because "threats remain present".
Interior Minister Bernard Cazaneuve announced that nearly 5,000 members of the security forces would be sent to protect France's 717 Jewish schools, and that troops would be sent as reinforcements over the next two days.
Prime Minister Manuel Valls said synagogues would also be protected, as would mosques, following some retaliatory attacks over the Charlie Hebdo killings.
Last week, Mr Valls admitted there had been "clear failings" after it emerged that the three gunman involved in the attacks - Said and Cherif Kouachi and Amedy Coulibaly - had a history of extremism.
The Kouachi brothers were on UK and US terror watch lists and Coulibaly had previously been convicted for plotting to free a known militant from prison. Coulibaly met Cherif Kouachi while in jail.
Coulibaly and the two brothers were shot dead on Friday after police ended two separate sieges.
Coulibaly killed four people at a kosher supermarket in eastern Paris on Friday before police stormed the building. He is also believed to have shot dead a policewoman the day before.
Ahead of Sunday's rally in Paris, a video emerged appearing to show Coulibaly pledging allegiance to the Islamic State militant group.
In the video, he said he was working with the Kouachi brothers: "We have split our team into two... to increase the impact of our actions."
The Kouachi brothers claimed they were acting on behalf of Yemeni branch of al-Qaeda (AQAP). But experts say it is highly unlikely that Islamic State and al-Qaeda, rivals in the Middle East, would plan an attack together.
The attacks in Paris started last Wednesday, when the Kouachi brothers raided the offices of the satirical magazine Charlie Hebdo, killing 12 people - including eight journalists and two police officers.
Mr Valls said on Monday that authorities thought that the attackers had at least one accomplice, for whom police are still hunting.
One suspect is Hayat Boumeddiene, Coulibaly's partner, though is believed to have left France before the attacks. The Turkish foreign minister said she had arrived in Turkey on 2 January from Madrid, before continuing to Syria six days later.
Mr Valls also said that a jogger shot in a separate attack in Paris on Wednesday which prosecutors have linked to Coulibaly was "between life and death".
In London, Prime Minister Cameron consulted senior intelligence and security officials on Monday over Britain's response to the attacks in France.