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Three Atlantic Forest endemic species of emerald dragonflies of the genus Navicordulia Machado & Costa, 1995 are reviewed through a morphological comparative analysis. All name-bearing types and additional specimens of the Navicordulia atlantica-complex-Navicordulia atlantica , Navicordulia mielkei Machado & Costa, 1995and Navicordulia miersi Machado & Costa, 1995were investigated to assess their taxonomic and nomenclatural status. Based on our results the hypothesis of these three nomina corresponding to distinct species is no longer supported. The proportional size of caudal appendages, an additional crossvein in cubito-anal space in the hind wing, as well as minor differences in coloration of pterostigma are not reliable diagnostic characters for supporting their specific status. We consider the three simultaneously available nomina as synonyms, and by action of the first reviser, Navicordulia atlantica Machado & Costa, 1995 is selected as valid nomen, hence N. mielkei syn. nov. and N. miersi syn. nov. are their subjective junior synonyms. Photos, other illustrations, and a new species-level diagnosis are given. Despite of the advances of taxonomic knowledge of Navicordulia, the second species-rich corduliid genus in the Neotropical region, the status of some species still necessitates a full revision.