The fairy tube-nosed bat, Murina tiensa, is considered to be endemic to Vietnam. It is known only from the original description, when it was found at two localities in limestone karst areas. In 2008, we conducted a series of intensive field surveys throughout the country and obtained additional records of this species from various habitats, including degraded to nearly pristine forests and an offshore island. Our results indicate that M. tiensa is a sexually dimorphic species, females being considerably larger than males in all external and craniodental measurements. The species emits broadband, downward frequency-modulated echolocation calls with a dominant first harmonic. When handheld or when flying in a flight tent, signals had a similar structure and were emitted in groups of 2–4 signals. On average, signals swept from 150 to 49 kHz in 2.2 ms for handheld bats, and, from 145 to 50 kHz in 1.9 ms for flying bats. M. tiensa often occurred in sympatry with M. cyclotis and several rhinolophids.