Mnium marginatum forms loose, 2 to 4 centimeters high lawns. These are light green in youth, brownish-green in age, rust-colored in the interior and matted slightly at the base. The upright to slightly curved stalks are loosely peeled. Sterile stalks are usually seemingly double-lined. The lanceolate leaves descending from the stalks are moist erect and protruding, dry slightly crimped, up to 5 millimeters long and 1.2 millimeters wide, with a slightly pointed pointed tip. The blade edge is lined and trimmed down to the middle of the blade with dull, rare pointed double teeth. The rib reaches into the tip of the blade and is usually smooth at the back. The blade cells are approximately round, 18 to 44 -m long and 16 to 33 -m wide.