Bats play essential roles in natural environment, particularly in agro-ecosystems. Over one thousand and two hundreds of bat species are found in the world. Among them, sixty two species are pipistrelles (Pipistrellus spp.). To date, a total of 108 bat species are known from Vietnam, including six pipistrelle species. They are commonly recorded in all forest, agro-ecosystem, and urban areas. However, Vietnamese pipistrelles have received very little from scientist. In fact, identification of these species normally meet with serious difficulties because of their similarity in morphological characteristics. With reference to materials and data obtained from recent surveys, this paper provides diagnoses of four selected pipistrelle species with supplemental infonnation about their ecology.