The genus Microbrachida was described by Alexander Bierig based on one tiny rove beetle. Since then, it has not been studied. Recently, a set of small rove beetle specimens were collected in the heart of the Brazilian Amazon, where they occur foraging mushrooms that grow on logs of cultivated trees. These mushrooms cause an infection known as witches' broom disease on those plants. Here, we redescribe Microbrachida and describe a new species in it. We also provide images of the diagnostic characteristics of the genus (including scanning electron micrographs), a key to the New World genera of Gyrophaenina, a key to the species of Microbrachida and a preliminary discussion about the potential biological control of the new species.