The species are among the 25 most endangered primates and are listed as in danger of extinction, with numbers in the wild thought to be as low as 1,000 in West Africa, where they have been depleted by deforestation and the illegal bush meat trade.
The baby monkey is the second generation to be born in the zoo as her mother Monika, was bred there in 2009 and had her first baby last year. The father, 12-year-old Racky, was transferred to Barcelona Zoo from Accra Zoo in Ghana two years ago.
Dr Maria Teresa Abelló, the conservation co-ordinator at the zoo, said the new arrival “reflected the success” of the captive breeding programme.
Barcelona has named August 1st Mangabey Awareness Day in a bid to raise awareness about the plight of the species.