<p>The insect spermatheca stores sperm in the female’s body after copulation. Despite its relevance for reproduction, the organ has been investigated in just a few species of mosquitoes. In this work, the morphology of the spermathecae of the mosquito <i>Lutzia bigoti</i>, a species with predatory larvae with potential use in the biological control of immature mosquitoes that are vectors of pathogens, was analyzed. In this species, the three spermathecae have round-shaped reservoirs (one large and two small), delimited by a multilayered cuticle and a thin epithelium. The spermathecal reservoir is connected to the proximal portion of the female reproductive tract by a long and narrow duct. This reservoir is lined with a tall epithelial cell layer and is surrounded by attached muscle fibers. Glandular cells associate with the reservoir wall, collectively forming a spermathecal gland located near the point of attachment of the spermathecal duct with the spermathecal reservoir. Additionally, glandular cells are individually attached to the duct. Glandular cells are associated with secretory cavities filled with an electron-lucent material, likely released towards the spermathecal lumen for sperm nourishment and maintenance. In <i>L. bigoti</i>, the spermathecae are similar to those of other Culicinae mosquitoes, suggesting a high degree of conservation throughout the evolution of this taxon.</p>