[1][2][3] Adults are small to moderate sized beetles, 3-35mm, with heavily sclerotized bodies that are either dorso-ventrally compressed (genera occurring under bark) or subcylindrical in cross section (genera inhabiting wood-borer tunnels).

Adults are generally brown or black, rarely with a color pattern, with prominent mandibles, confluent gular sutures, thick, moniliform antennae (antenna with equally sized spherical segments that looks like a string of beads), unequal tibial spurs on the front legs, and generally a characteristic system of grooves and/or carina on the dorsal surface.

Later instar larvae are physogastric (swollen posteriorly), with simple setae, short unsegmented legs, and reduced mouthparts.

Only Passandra Dalman occurs in both the Old and New Worlds, being represented in the Neotropical region by a single species, P. fasciata (Gray).

The oldest record of the family is Mesopassandra, from mid-Cretaceous (latest Albian-earliest Cenomanian) aged Burmese amber from Myanmar, around 100 million years old, which is placed in its own subfamily as the most primitive known member of the group.