Hollande, who was visiting Greece on Tuesday, said the seven were a family and the French embassy in the Cameroonian capital, Yaoundé, said that there were two girls and two boys.
The kidnappers were on motorbikes, the embassy said, when they grabbed the family in Dandanga, near the Nigerian border.
They visited the Waza nature reserve on Monday and slept in a camp there overnight before leaving Tuesday morning, a source there told the AFP news agency.
The kidnapping is the first of Western tourists in Cameroon.
A French engineer was kidnapped in Nigeria in December and seven other foreigners were captured there on Saturday.