Updated distribution data are presented for the following species of Notonectidae (Heteroptera) in southeastern Asia: Anisops breddini Kirkaldy, 1901, A. kuroiwae Matsumura, 1915, A. nasutus Fieber, 1851, A. nigrolineatus Lundblad, 1933, A. occipitalis Breddin, 1905, A. rhomboides Nieser & Chen, 1999, A. stali Kirkaldy, 1904, Aphelonecta philippina Zettel, 1995, Enithares bakeri Brooks, 1948, E. freyi Brooks, 1948, E. intha Paiva, 1918, E. mandalayensis Distant, 1910, E. martini martini Kirkaldy, 1898, E. quadrispinosa Lansbury, 1967, E. sinica (Stål, 1854), E. subparallela Lansbury, 1968, E. uncata Lundblad, 1933, E. cf. vicintricata Lansbury, 1968, and Nychia sappho Kirkaldy, 1901. There are six fi rst records from Brunei Darussalam (Anisops breddini, A. nasutus, A. nigrolineatus, Aphelonecta philippina, Enithares cf. vicintricata, and Nychia sappho) and one fi rst record each from the Philippines (Anisops occipitalis), China (Enithares mandalayensis), West Malaysia (Enithares sinica) and East Malaysia (Sarawak) (Enithares uncata). A short description of the previously unknown female of Enithares intha is given. The status of Enithares quadrispinosa as a separate species (not a subspecies of E. freyi) is confi rmed. Check-lists of the Notonectidae of the Philippines and Brunei are provided.