Congenital hypofibrinogenemia is a rare disorder caused by heterozygous mutations in one of the three fibrinogen genes--fibrinogen α-chain (FGA), fibrinogen β-chain (FGB) and fibrinogen γ-chain (FGG)--which code for the Aα, Bβ and γ chains, respectively. In this study, we identified a genetic defect in the FGG underlying the hypofibrinogenemia. The proposita had a prolonged blood clotting time (thrombin time 24.5 s, prothrombin time 16.8 s) and a low level of plasma fibrinogen (0.71 g/l by Clauss method and 0.79 g/l by immunoturbidimetry). DNA screening of the whole fibrinogen gene revealed a heterozygous GC mutation at nucleotide 7482 in her FGG gene. Her father and her half-brother are also heterozygous for this mutation. This mutation contributes to Thr277 → Arg in the γ chain of fibrinogen. To the best of our knowledge, this is the first report of such a mutation that is associated with hypofibrinogenemia.