To understand that an object has changed state during an event, we must represent the before' and after' states of that object. Because a physical object cannot be in multiple states at any one moment in time, these before' and after' object states are mutually exclusive. In the same way that alternative states of a physical object are mutually exclusive, are cognitive representations of alternative object states also incompatible? If so, comprehension of an object state-change involves interference between the constituent object states. Through a series of functional magnetic resonance imaging experiments, we test the hypothesis that comprehension of object state-change requires the cognitive system to resolve conflict between representationally distinct brain states. We discover that (1) comprehension of an object state-change evokes a neural response in prefrontal cortex that is the same as that found for known forms of conflict, (2) the degree to which an object is described as changing in state predicts the strength of the prefrontal cortex conflict response, (3) the dissimilarity of object states predicts the pattern dissimilarity of visual cortex brain states, and (4) visual cortex pattern dissimilarity predicts the strength of the prefrontal cortex conflict response. Results from these experiments suggest that distinct and incompatible representations of an object compete when representing object state-change. The greater the dissimilarity between described object states, the greater the dissimilarity between rival brain states, and the greater the conflict.