Sedenia mesochorda is a moth in the Crambidae family. It is found in Australia, where it has been recorded from Victoria. The wingspan is about 22 mm. The wings are whitish, densely suffused with pale fuscous. There is a median whitish streak from the base to the end of the cell. The hindwings are whitish, faintly suffused with fuscous along the apical portion of the termen.