Otolith oxygen (δ^(18)O) and carbon (δ^(13)C) stable isotopes of grey mullets (Mugil cephalus) were analyzed to reconstruct their migratory history. Juvenile mullets collected in coastal water had otolith δ^(18)O values of approximately (-0.8per mille), representing their marine residence. Otolith δ^(18)O values decreased by approximately (3per mille) after the transplantation of wild juveniles into aquaculture ponds with constant low salinity for 1 month. Fish in captivity from the juvenile to adult stage showed seasonal cycles of δ^(18)O values, reflecting the annual variation of water temperature. Cyclic otolith δ^(13)C was also observed in the reared mullets, which might reflect the seasonal variation of dissolved inorganic carbon in the ponds. Two types of migratory history were found in wild adult mullets according to their otolith isotopic profiles. Type 1 mullets migrated to freshwater after hatching in the sea and returned to high salinity environments in estuaries or the sea. Some individuals moved to estuaries or the sea during the first winter of their life, but some stayed longer in estuaries before their migration to the sea. By contrast, type 2 fish showed higher δ^(18)O (＞(-6per mille)), which suggests that the mullets spent most of their time moving between estuary and sea water without entering rivers. This study demonstrates that stable isotope analysis of otoliths is a useful tool for investigating the migratory life histories of grey mullets.