"Mutual exclusivity" is the assumption that each object has only one category label. Prior research suggests that bilingual infants, unlike monolingual infants, fail to adhere to this assumption to guide word learning. Yet previous work has not addressed whether bilingual infants systematically interpret a novel word for a familiar object (i.e. an object with a known category label) as a second category label. We addressed this question by exploring bilingual and monolingual infants' use of mutual exclusivity in a task in which they heard a novel label for a familiar object with a salient color (e.g. an aqua-colored dog). They were subsequently tested with two trials that probed whether they interpreted the word as a second category label for the object (e.g. another word meaning "dog") or as a label for one of the object's salient properties, namely its color (e.g. a word meaning "aqua"). Bilingual infants failed to adhere to mutual exclusivity and interpreted the novel word systematically as a second object category label for the familiar object. In contrast, consistent with their use of mutual exclusivity, monolingual infants rejected the novel word as a second category label, and instead showed some evidence of interpreting it as a property (color) term for the familiar object. The findings suggest that both bilingual and monolingual infants are systematic in their interpretation of a novel label for a familiar object, but that they show different interpretations of that label. We thus argue that theoretical accounts of early word learning must consider the crucial role of linguistic experience.