A dialogue system for a vehicle may include: a storage storing context information including at least one of vehicle state information indicating a vehicle state, user information indicating a driverof the vehicle, or driving environment information indicating a driving environment of the vehicle; an input processor determining whether a context of the vehicle is a pre-utterance context, in whichthe dialogue system firstly outputs an utterance, based on the stored context information, determining whether a task related to the pre-utterance context is a duplicate task which has already processed or is currently processing when the context of the vehicle is the pre-utterance context, and obtaining at least one of an action corresponding to the pre-utterance context or a pre-utterance message to be output by the dialogue system when the task related to the pre-utterance context is not a duplicate task; a dialogue manager obtaining, from the storage, a parameter value of an action parameter used to perform the action corresponding to the pre-utterance context when the input processor obtains the action corresponding to the pre-utterance context; and a result processor generating a dialogue response.