"In order to respond to the urgent need expressed by the Kurdistan regional authorities, the president has decided, in agreement with Baghdad, to deliver arms in the coming hours," Hollande's office said in a statement.
"France intends to play an active role by providing, along with its partners and in liaison with the new Iraqi authorities, all the assistance required," the statement added.
Over the weekend, Paris already provided 18 tonnes of humanitarian aid and a new shipment of 20 tonnes of aid was due to arrive in northern Iraq later on Wednesday.
Hollande reiterated France's support for Iraq's premier designate Haidar al-Abadi and urged a "unity government, representing all Iraqis to fight effectively against Islamic State."
The French leader said the population in Kurdish areas of Iraq was facing a "catastrophic situation" which "called for the continuation and intensification of efforts by the international community."
"For several days, France has taken the necessary measures to support the operational capabilities of the forces fighting Islamic State," Hollande stressed.
France has been pushing for days for an emergency meeting of EU foreign ministers to coordinate a European response to the crisis in Iraq, notably in terms of delivering arms.
EU foreign affairs chief Catherine Ashton announced on Wednesday that she was prepared to convene such a meeting "as early as this week" and was checking with member states whether this was possible.
On Tuesday, Britain said it would transport military supplies from other countries to Kurdish forces battling the militants amid Western fears the crisis could spread throughout the region.
On Wednesday Iraq's Prime Minister Nuri al-Maliki continued to defy international pressure to step aside to forward reconciliation and the fight against militants.
Humanitarian crisis deepens
The United States has carried out air strikes against members of the Islamic State (IS) jihadist group in the area of Mount Sinjar, where the UN refugee agency says up 20,000-30,000 people, many of them members of the Yazidi minority, are besieged.
Thousands more poured across a bridge into Iraq's autonomous Kurdish region on Wednesday after trekking into Syria to escape, most with nothing but the clothes they wore.
Some women carried exhausted children, weeping as they arrived to the relative safety of Iraqi Kurdistan.
But there are still large numbers on the mountain, said 45-year-old Mahmud Bakr.
"Many of them are elderly; they cannot walk this distance," Bakr told AFP.
"My father Khalaf is 70 years old - he cannot make this journey. But up there, there is very little food and no medicine," he said.
UN minority rights expert Rita Izsak has warned they face "a mass atrocity and potential genocide within days or hours".
US Secretary of State John Kerry said Wednesday that Washington is looking at options to bring the trapped civilians out.
"We will make a very rapid and critical assessment because we understand it is urgent to try to move those people off the mountains," he said.