Most are marine, though a few needlefish and halfbeaks inhabit brackish and fresh waters.

[3] The order is sometimes divided up into two suborders, the Adrianichthyoidei and the Belonoidei, although this clade is referred to as Exocoetoidei in the 5th edition of Fishes of the World.

Originally, the Adrianichthyidae were included in the Cyprinodontiformes and assumed to be closely related to the killifish, but a closer relationship to the beloniforms is indicated by various characteristics including the absence of the interhyal, resulting in the upper jaw being fixed or not protrusible.

The Scomberesocoidea contain the Belonidae and Scomberesocidae, while the Exocoetoidea comprise the Exocoetidae, Hemiramphidae and Zenarchopteridae.

The basal condition in the order excluding the ricefishes is an elongated lower jaw in juveniles and adults as represented in halfbeaks.