This study describes the seasonal reproductive cycle, gonad structure, and sex ratio of the Anodonta gabillotia pseudodopsis. A total of 300 individuals was collected in monthly samples from September 2005 to August 2006 in Göolbaşi Lake, Turkey. Calculation of the gonadosomatic index and histological examination of the gonads showed that gametogenesis began in winter and spawning occurred in summer and early autumn. Although, sex ratios of Anodonta gabillotia pseudodopsis were not significantly different from the expected 1:1 ratio (P > 0.05), slightly female biased sex ration were recorded. Although mature oocytes and spermatozoa were present for almost the entire year, gonadal activity seemed lowest in October and December, when gonad recovery and reorganization were more evident than gametogenesis. Both sexes displayed greatest gonad activity during the summer months of the year. Three types of gonads were identified, which varied according to the proportion of gametogenic tissue. According to our morphologic and histologic observation, Anodonta gabillotia pseudodopsis were classified as accidental or abnormal hermaphrodite (typically in dioecious species) species. The hermaphroditic specimens of A. pseudodopsis had gonads composed predominately of tissue of only female. These results suggest that under certain environmental conditions females may become hermaphrodites and self-fertilization occur.