A new species of Bachia of the B. heteropa group is described from the Parque Nacional Montanhas do Tumucumaque in northeastern Amazonia, Amapá State, Brazil. The new species morphologically resembles B. heteropa and B. guianensis. Nonetheless, the absence of interparietal and prefrontal scales, and the number of supraciliary scales, can distinguish the new species from its close relatives. This description increases the species diversity of the B. heteropa group after a number of decades of stasis in the taxonomy of this group in Amazonia. In addition, we present an updated key to the groups of Bachia, including the species and subspecies of the B. heteropa group.