Eleocharis montevidensis is a rhizomatous perennial herb forming tufts or mats of erect, firm stems up to half a meter tall. The narrow grasslike leaves are dark purplish or reddish brown at the bases, becoming lighter in color toward the tips, and drying to a thin, papery texture. The inflorescence is an oval-shaped spikelet appearing at the tip of the stem. It is under a centimeter long and made up of several flowers covered in brownish bracts.
Eleocharis montevidensis have often been called either E. montana or E. palmeri in some North American publications.