Roosts in caves, clinging to walls in areas of twilight closer to the entrance, and in the same structures but separate from other species of Emballonura and Mosia nigrescens. It occurs in tropical forests, flying in open spaces in and around the tree canopy (Bonaccorso 1998; K.N. Armstrong unpublished data).
Their echolocation call is distinctive, and is typically recorded less often than other small emballonurid species. Pulse shape resembles that of Hipposideros, but the strongest second harmonic has a characteristic frequency of c. 35 kHz, which is around the same frequency of the first harmonic of the common species Mosia nigrescens, so E. dianae can be distinguished on the basis of a first harmonic at c. 17 kHz (K.N. Armstrong, unpublished data).

This species occurs in Papua New Guinea (in Gulf Province, Hela Province, Sandaun Province, Southern Highlands Province and Western Province; and New Britain and New Ireland in the Bismarck Islands) and the Solomon Islands (the islands of Guadalcanal, Rennel, Malaita, and Santa Isabel, and possibly some others) (Flannery 1995a,b; Bonaccorso 1998; K.N. Armstrong unpublished reports). It ranges from sea level to 1,400 m asl (Mu, East New Britain Province).

Suitable conservation actions for this species are the protection of known roosting caves, and identification of additional important roosting sites. There are no known records of this species from protected areas, but it may occur in some within its range in Papua New Guinea.