Spermiogenesis and mature spermatozoa of the Korean false minnow Pseudogobio esocinus (Cyprinidae) are described by means of scanning and transmission electron microscopy. Spermiogenesis is characterized by lateral development of the flagellum, absence of nuclear rotation, and eccentric nuclear fossa formation. The spermatozoa have a spherical head containing a nucleus with highly condensed chromatin and no acrosome. The nuclear fossa contains the proximal centriole and anterior part of the distal centriole. The midpiece is type A II and contains semi-fused mitochondria around the axoneme. However, the symmetrical distribution of 4 or more the mitochondria does not follow a general pattern of the cyprinid spermatozoa. Cytoplasmic vesicles in the midpiece are common in Cypriniformes and some of Siluriformes and Characiformes spermatozoa.