[1] Molecular phylogenetic studies mostly (but not always) place the family in the order Chlorellales, as sister to Chlorellaceae.

Members of Oocystaceae are common microalgae in freshwater habitats, and a few occur in semi-saline.

[3] Members of the family Oocystaceae consist of cells which are solitary or found in colonies of 2, 4, 8, 16, or more.

Cells are typically oval to ellipsoidal, sometimes spherical, rhomboid, spindle-shaped or lemon-shaped.

The cell wall is multilayered, often thickened at the poles, and may be smooth, warty or covered in spines.