Filamentous thalli are macroscopic or microscopic. The thalli of the Compsopogonaceae are differenciated into axial and cortical cells. Simple pit connection is present only in the Compsopogonaceae. Cell possesses a single or many chloroplasts that are red to blue-green in color. Pyrenoid is absent. Low molecular weight carbohydrates are florideside. Compsopogonalean algae are reproduced by monospores but sexual reproduction is unknown. They inhabit in freshwater to brackish water.