The purpose of this paper is to investigate a possibility of applying multi- methodological approach for solving a dilemma. The motivation of this attempt is that the two different approaches, the system dynamics and the theory of constraints, resemble each other in having mental models for describing the target system and using graphic tools for representing those mental models. After a brief discussion on the comparison of the two approaches, a combined method applying to the problem of dilemma is suggested. For an experimental example, the proposed approach is applied to the sales and finance conflict on an inventory issue. The study shows that the suggested approach is able to complement each other`s drawbacks. Especially constructing a stock-and-flow model and implementing a computer simulation would be very useful for quantifying the system`s behavior which is hardly tracked down when applying the theory of constraints alone.