Dero zeylanica is a medium-sized worm with light brownish in color, with yellowish ends. The prostomium is triangular in shape and bears hairs, with the tip blunt and slightly directed upwards. Eyes are absent. The number of body segments varies from 50 to 68, followed by some undifferentiated posterior segments and a branchial organ. The mouth is positioned on the ventral side, transversely elongated. The dorsal setae bundle begins in segment VI, typically containing 1-3 hairs and 1-3 needles per bundle.