Although many anecdotes suggest that creative insights often arise during mind wandering, empirical research is still sparse. In this study, the number reduction task (NRT) was used to assess whether insightful solutions were related to mind wandering during the incubation stage of the creative process. An experience sampling paradigm was used to provide an online measure of mind wandering while participants performed a sustained attention response task (SART). Participants were 91 Chinese college students. The results showed that participants who gained insights of the hidden regularity in the NRT (or the "solvers") reported significantly more mind wandering during incubation than those who did not gain insights (or the "non-solvers"). Moreover, the solvers also rated themselves higher in overall creativity on the Exercise in Divergent Feeling (Williams, 1979) than did the nonsolvers. The two groups, however, did not differ in other characteristics, such as working memory capacity and motivation. These results suggest that mind wandering may play an important role in solving insight problems.