Mind wandering has been investigated in a variety of sustained attention tasks. In the present research, we investigated the role of mind wandering while listening to familiar or unfamiliar musical excerpts, and its effects on linguistic processing. Participants performed a lexical congruity task involving judging the semantic relatedness of a list of word pairs while listening to familiar classical music, unfamiliar classical music, or non-music environmental sound clips. Mind wandering episodes were probed randomly and intermittently for participants to self-report their mind wandering episodes during the task. Results showed that listening to familiar music is associated with faster response times and lower frequency of mind wandering. Whereas mind wandering episodes tend to be more frequent when participants listened to unfamiliar music. Implications from previous attention models and theories of music familiarity suggest that familiar music might increase task enjoyment without compromising behavioral performance.