In this study, the occurrence of a parasitic helminth infecting a Turkish endemic fish, Manyas spirlin, Alburnoides manyasensis from the Niltifer stream, Bursa, was studied from winter 2017 to autumn 2018. A total of 46 A. manyasensis were examined for the presence of the helminth. The helminth was identified as Paradiplozoon homoion (Monogenea: Diplozoidae) and occurred on the gills of host fish. A total of 115 specimens of P. homoion infected 32 of 46 fish examined, with prevalence and mean intensity of infection of 69.57% (41.67% in Summer to 90.00% in Winter) and 3.59 (1.00 in Summer to 6.22 in Winter) respectively. Additionally, prevalence and mean intensity of infection was calculated per seasons, host size and sex. The highest values for prevalence and intensity of infection were found in winter for P. homoion. To our knowledge, this is the first ichthyoparasitological study for A. manyasensis in Turkey. This is also the first record of P. homoion from this host fish and locality.