A new species belonging to the genus Ooencyrtus Ashmead is described. Ooencyrtus marcelloi sp. nov. has been reared from eggs of Heliconiini (Lepidoptera: Nymphalidae, Heliconiinae) collected in Panama on Passiflora spp. The new species is compared with its closest Ooencyrtus species, i.e. O. caligo Noyes, O. neustriae Mercet, O. flavipes (Timberlake), O. camerounensis (Risbec), O. endymion Huang and Noyes and Ooencyrtus sp. “undet. C.” (from India). This represents the second record of Ooencyrtus from Heliconinae and the first record of this genus from Panama.