Research summary: Mental models, reflecting interdependencies among managerial choice variables, are not always correctly specified. Mental models can be underspecified, missing interdependencies, or overspecified, containing nonexistent interdependencies. Using a simulation model, we find that under‐ and overspecification have opposite effects on exploration, and thereby, performance. The effects are also opposite, depending on whether a manager controls all choice variables. The mechanism underlying our results is a feedback loop: misspecified mental models influence managerial learning about the effectiveness of choices; this learning guides how the environment is explored, which in turn, affects which information will be generated for future learning. We explore implications of these results for strategic management and introduce the notion of “cognitive fit” between the mental model of the decision‐maker and the strategic environment. Managerial summary: Managers often rely on mental models to guide their decision‐making. These mental models, however, are often misspecified, that is, more or less complex than the situation managers are facing. Using a simulation model, we study the consequences of such misspecified mental models. We find that the performance implications of misspecified mental models crucially depend on whether the manager controls all choice variables. We identify situations in which simpler mental models are better than overly complex ones, and vice versa. Copyright © 2015 John Wiley & Sons, Ltd.