<p>People often turn to their smartphones when they feel bored. Considering that emotion beliefs play an important role in emotional experience and regulation, do people who strongly dislike boredom use their smartphones more often to avoid this state? The current research investigated both individual differences and intrapersonal fluctuations in a lay belief about boredom—boredom dislike—alongside experienced boredom and smartphone use. We conducted a correlational study (Study 1; <i>N</i> = 495) and a three-wave longitudinal study in which participants completed surveys every four months (Study 2; <i>N</i> = 261). Smartphone use was assessed via both self-report measure and screentime tracking. Across both studies, boredom dislike predicted not only more frequent and intense experiences of boredom but also more smartphone use. Participants who reported stronger boredom dislike also reported higher levels of excessive smartphone use. At the within-person level, occasions when participants disliked boredom more than usual were associated with longer screen time. Furthermore, boredom dislike moderated the association between boredom and smartphone use. At the between-person level, the positive associations of boredom frequency and intensity with excessive smartphone use were more salient among those who strongly disliked boredom. At the within-person level, boredom frequency positively predicted screen time only among participants low in boredom dislike; among those high in boredom dislike, screen time remained elevated regardless of boredom frequency. Overall, our findings suggest that an aversive orientation toward boredom may motivate smartphone use. We discuss their implications for boredom coping and digital media use.</p>