Drosera thysanosepala is a scrambling sundew endemic to the sandy heathland north of Perth. The species is named after its fringed sepal margins (thysanotos = fringed, sepalum = sepal).

Drosera thysanosepala has a glabrous, scrambling stem that reaches up to 40cm in height. This stem is extremely thin near the ground, switching directions at each sequential leaf node. The stem thickens slightly a few nodes from the ground. The leaves on the upper portions of the plant are produced in sets of three, with the central leaf having a very long petiole. The central leaf attaches to surrounding bushes to elevate the stem. The sepals are glabrous and coloured greenish-yellow to red. The petals are white or pink.

The species grows in deep, well-drained sand amongst sparse heathland. It is distributed in the sand plains north of Perth up to Kalbarri.

The species is a member of the Drosera menziesii complex, which all have glabrous stems and orbicular laminae. Drosera thysanosepala is distinguished from all its relatives by its sepals, which are glabrous. It can grow alongside the very similar Drosera drummondii which shares a long, scrambling stem, but has hairy sepals. The plants grow up to 40 cm long and rely on surrounding vegetation for support (in contrast to D. menziesii and D. basifolia, which are self-supporting).