The meeting of chiefs of defence staff from Nigeria, Niger, Chad and Cameroon, plus a high-level military official from Benin, came before talks between heads of state and government on Thursday.
In Paris, Benin's President Thomas Boni Yayi promised Thursday's meeting would be "decisive" in the fight against the Islamists, whose six-year insurgency has claimed at least 15,000 lives.
His Nigerian counterpart Muhammadu Buhari has made crushing the group his new administration's top priority and there has been a flurry of activity on the subject since he took power on May 29.
The military meeting was designed to determine strategies for a new, African Union-backed regional force against the rebels, Nigeria's military said in a statement on Monday evening.
As talks opened, chief of defence staff Alex Badeh said it pointed to the countries' "common resolve to work together to put an end to a menace that has become a regional and... global problem".
"If there is any time for us to rise in one voice irrespective of our differences, it is now," he added.
In the meantime, troops from Nigeria, Chad, Niger and Cameroon have been fighting Boko Haram insurgents in northeast Nigeria for several months and have claimed a series of successes.
Defence ministers from all five countries are due to meet in Abuja on Wednesday.
In his inaugural speech, Buhari, a former army general, announced the transfer of the military command centre from Abuja to the strategic city of Maiduguri, in the rebels' northeast stronghold.
On a visit to the French capital for talks with President Francois Hollande, Boni Yayi said Thursday's regional summit would be "decisive" and praised Buhari's leadership on the issue.
