Multiobjective reservoir operations are generally complex, as they are often associated with a large quantity of uncertain factors in combination with noncommensurable objectives. In this study, fuzzy-state stochastic dynamic programming (FSDP) and multicriteria decision-making (MCDM) are integrated to derive operating rules for a single multiobjective reservoir operation problem. The model addresses uncertainties due to randomness in inflows and imprecision in variables' discretization and objectives. The FSDP model takes into account uncertainties due to the random nature of inflows and imprecision due to variable discretization. Imprecise and noncommensurable objectives are quantified by a set of subjective criteria, the aggregation of which is performed through an MCDM model, by which possible decisions at every stage of the FSDP model are evaluated and compared. The proposed approach is then employed in deriving operating rules for the Karoon 1 reservoir in south-west Iran and the rules are tested and evaluated through simulation. Results show the model's capability in handling different kinds of uncertainties involved in real reservoir operation problems.