A new species of the two-tailed small minnow mayfly genus Acentrella Bengtsson (Ephemeroptera: Baetidae) is described as Acentrella nadineae, new species, based on highly distinctive larvae taken from high quality streams in southern and eastern Ohio. The species is differentiated by a short tibia tarsus of the forelegs; long, evenly spaced, moderately dense setae along the dorsal edge of the femora; highly asymmetric gills with mediobasal markings; no dorsomedial abdominal projections; no developed hindwingpads; and typically a relatively dark abdominal tergum 7 and light abdominal tergum 8. The new species is also reported from North Carolina, and sometimes co-occurs with the more common and widespread, but similarly sized A. turbida (McDunnough).