There was no immediate claim of responsibility for the attack on Tuesday, which staff said also wounded 10 other people.
But a jihadist insurgency originating in the Sahel region has spread to parts of coastal West Africa, including northern Benin.
“Yesterday… a team of rangers was ambushed in W National Park in Benin,” said African Parks, a non-profit group that has managed the park since 2020.
They were conducting a patrol at the northern limit of the park where it intersects with Burkina Faso and Niger, it added.
“Initial reports indicate that… five rangers and one member of the Benin Armed Forces have been killed, with 10 more injured,” it said.
African Parks said military reinforcements and additional rangers had been deployed to the area, but Beninese authorities did not immediately comment on the incident.
Benin’s army has reinforced its presence in the north since what military sources said were the first two jihadist attacks in the country late last year.
Last month, two Beninese soldiers were killed when their vehicle hit a makeshift bomb in the country’s northern Atakora area.