Drosera thysanosepala is a scrambling sundew endemic to the sandy heathland north of Perth. The species is a member of the Drosera menziesii complex, which all have glabrous stems and orbicular laminae. Drosera thysanosepala is distinguished from its relatives by its sepals, which are glabrous. It also has a distinctive lower stem, which is extremely thin and threadlike. 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).