Cryptobia neghmei sp.n. is described from the blood of two species of flounder, Paralichthys microps and P. adspersus, inhabiting the Chilean coast in the southern Pacific Ocean. Flagellates were elongate, slender, with two flagella and a conspicuous undulating membrane. It was distinguished from previously described species on the basis of its unusual shape and dimensions. All of 97 flounder were infected upon examination. Developmental stages of kinetoplastid protozoans, perhaps C. neghmei sp. n., were observed in some leeches Glyptonotobdella sp. that were found attached to flounder, which probably represent a mode for transmission among piscine hosts