The hoary elfin butterfly has a wingspan of one inch. The upperside of its wings is dark brown. The underside of the wings is dark brown close to the body and gray-violet away from the body. There is no tail on the hindwing, which helps to distinguish this species from some other elfin species.
In Illinois, this species can be found in the dunes along Lake Michigan where the bearberry (Arctostaphylos uva-ursi) plant grows. Both bearberry and the hoary elfin are endangered in the state. Bearberry is the host plant for the larvae of this butterfly. Adults are active from April to May. The species overwinters as a chrysalis. Northeastern Illinois is at the edge of the range for this butterfly.