Abstract We examined the effect of tributyltin (TBT) on reproduction of the pearl oyster (Pinctada fucata martensii). In a maternal exposure test, five female pearl oysters were exposed to TBT at measured concentrations of 0 (control), 0.092, or 0.191 μg/L at 25°C for one week, and the embryo developmental success (the ratio of normal D-larvae to all larvae) was measured. The embryo developmental success was significantly decreased in the 0.191-μg/L treatment group (65.5%) compared to that in the control group (82.5%; p = 0.031). Concentrations of TBT in the ovary reached 0.088 μg/g in the 0.191-μg/L treatment group. In a waterborne exposure test, inseminated eggs were exposed to TBT at measured concentrations of 0 (control), 0.020, 0.045, 0.091, 0.192, or 0.374 μg/L for 24 h. The embryo developmental success also was significantly decreased in the 0.192-μg/L treatment group (78.3%; p = 0.020) and no development at all was observed in the 0.374-μg/L treatment group compared with that in the control group (95.4%). These results clearly demonstrate that TBT accumulating in the bodies of bivalves has the potential to inhibit reproduction.