Galeopsomyia fausta LaSalle (Hymenoptera: Eulophidae) is a Neotropical eulophid solitary ectoparasitoid of the immature stages of Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae). In Central and South America, the activity of this wasp has resulted in good biological control of P. citrella. Characterization of the immature morphology of parasitoids is important for the identification to the species level before adult emergence and for the quantification of the impact of these natural enemies in biological control programs. This article reports our study of the immature stages of G. fausta from a laboratory colony maintained on P. citrella that were examined using scanning electron microscopy (SEM). The wasp has a typical hymenopteriform egg attached to the leaf chamber where P. citrella pupates. The parasitoid has three instars, very similar to each other, holopneustic, hymenopteriform, and 13-segmented. Its cuticle has multiple spines. The cranium is conspicuous and has a mandibulate suctorial mouth. On completion of its larval development an exarate pupa is produced. The distinctive attachment of the egg to the leaf and typical pupal morphology allow the identification of this parasitoid by using a binocular microscope, but identification of the larvae requires SEM.