Paracomesoma elegans sp. n., Paracomesoma lissum sp. n. and Gomphionema parvum sp. n. from sediments of river beds of the Mekong River Delta in Vietnam are described and illustrated. P. elegans sp. n. is characterized by its comparatively small body (L= 1042-1320 µm), comparatively narrow labial region (7-9 µm wide), short cephalic setae (3.5-4.5 µm long) and long and thin spicules (125-165 µm long). P. lissum sp. n. is characterized by its comparatively slender and medium size body (L=1338-1784 µm, a =28-36), short cephalic setae (6-7 µm long), 45-47 papilloid precloacal supplements and thin 88-98 µm long spicules in males. G. parvum sp. n. is characterized by its comparatively short and thick body (L=587-803 µm, a= 15-21), typical annulation of cuticle without its lateral differentiation, papillae-like labial sensillae, well developed stoma with big dorsal tooth; large, muscular and well developed pharynx bulb, double gubernaculum in two parts and two lateral bodies, presence of 16-21 cup-shaped precloacal supplements and elongate-conoid, comparatively thick tail.