They are endemic of the New World with a Nearctic-Neotropical distribution where a large fraction of the diversity of Opiliones are represented by this single family.

Cosmetidae have the northern extent of their range into the USA, where a small number species occur in the southern states.

Cosmetidae are prevalent in Amazonian region, but only relatively few also occur in Brazilian Atlantic Forest.

This family comprises members that may have elaborate white or yellow (but rarely also green/orange/red) markings such as stripes and spots on the dorsal body and peculiar pedipalps strongly compressed and applied on the chelicerae.

Attempts to organize the family in supra-specific units are hindered by the poorly resolved basic taxonomy.