Hirudinaria manillensis is a relatively large and robust leech, characterized by its elongated and soft body, flattened from top to bottom. Its dorsal surface exhibits a light brown coloration, while the ventral side appears pale greenish. The dorsum is adorned with four pairs of olive-green stripes. The oral sucker, which includes the prostomium and a few anterior body somites, is oval-shaped and features a cup-like pre-oral chamber that points downwards. The leech has five pairs of eyes and a lip with a median ventral fissure. Its jaws are notably large and adorned with prominent papillae. The gonopores are separated by five annuli, and the anus is a small aperture located mid-dorsally at the base of the posterior sucker.