A small bat that roosts in buildings and flies over familiar places after sunset.
Its back is grayish olive and its underside grayish brown; the ears are thin.
An urban survey in 2000–2001 used bat detectors to compare flight activity. Activity was recorded most often over water, next in open spaces, and least in secondary woodland. The authors suggested that woodland may hold many insects but its enclosed airspace could make flight harder.
Detections also shifted with season and sunset temperature: activity was recorded in February when the temperature exceeded 15°C, rose as temperatures increased, dipped from mid-May into early July, then rose again from late July into early September. In December, activity was not recorded when temperatures fell below 15°C. The recorded counts were detections of flight activity, not individual bats.
An extinction-risk assessment has not been added yet.
The Japanese Ministry of the Environment’s 2020 mammal Red List does not include the Japanese pipistrelle. In March 2026, the Ministry said the 2020 edition remained the latest assessment for terrestrial animal groups such as mammals.