Macarthuriaceae are rigid or wiry, rush-like herbs or subshrubs with green stems and reduced leaves.

[2][5] The small flowers have five perianth members, sometimes also five "petals", and eight stamens fused at the base.

[5] In 2009, Macarthuria was placed with Limeum in the Limeaceae, based on its morphology, but at that time no molecular material of Macarthuria had been examined.

[6] Prior to this, Endress and Bittrich had placed it in the family Molluginaceae.

[7] However, in 2011, molecular evidence was published, showing that Macarthuria is sister to all core Caryophyllales.