I observed mobbing of Glaucomys volans (Southern Flying Squirrel), upon removal and release from nesting boxes designed for them, by various bird species (1–9 total individual birds) on 33 occasions during winter surveys for the squirrels in southeast Ohio. I observed instances of mobbing by 1–3 species of primary and/or secondary cavity-nesting songbirds and woodpeckers. Mobbing behavior included flights within 1–2 m of a flying squirrel briefly positioned on a tree trunk as well as vocalizations. Mobbing episodes lasted 5–180 seconds, which largely depended on the amount of time a flying squirrel remained visible before retreating into a natural cavity. In light of the mobbing response reported here, perhaps more consideration should be given to the potential impacts that Southern Flying Squirrels may have on bird communities.