Atherina boyeri (Risso, 1810) has established abundant and successful populations in inland waters in Anatolia, although it is known as a marine species. In this study, the growth and reproduction properties of A. boyeri in the Hirfanli Reservoir were studied. Age determinations based on scale readings showed that the population had a 4-year life cycle. Sampled individuals ranged between 5.76 and 115.65 mm in total length and 0.01 and 10.48 g in total weight. The von Bertalanffy growth parameters for females were L-infinity = 156.78, k = 0.197, and t(0) = -0.197; for males, L-infinity = 151.02, k = 0.148, and t(0) = -0.148. Mean condition factor values, estimated from eviscerated weight, varied between 0.49 and 0.60. The length-weight relationship of A. boyeri indicated allometric growth, whereas the b value for females, males, and juveniles was 3.29, 3.23, and 3.50, respectively. The sex ratio was 1:1.14 in favor of females. The reproductive season, evaluated by the gonadosomatic index, extended from May to July. Mature egg diameter ranged from 0.64 to 1.73 mm. The mean total fecundity increased with age. In the Hirfanli Reservoir, certain life-history features of A. boyeri, such as short life cycle and increasing fecundity, indicated that this species has the potential to become dominant in freshwater systems.