Objective: The purpose of this study was to investigate the efficacy of a mindfulness-based intervention among college students with externalizing behaviors and attentional problems. Participants: Three students attending their first year in college received mindfulness-based stress reduction (MBSR) intervention and data were collected pre-intervention, during the intervention, post-intervention, and follow-up. Methods: The study utilized a single-case design (SCD). Data were collected via the Conners continuous performance test, Third Edition (CPT-3), the Conners Continuous Auditory Test of Attention (CATA), the Behavioral Assessment Scale for Children, Flex Monitor, Third Edition (BASC-3 FM), and the Mindfulness Attention Awareness Scale (MAAS). Results: Data were analyzed by calculating standard error of the difference, reliable change index, non-overlap of all pairs (NAP), and Tau-U. Conclusions: The results of this study strongly suggest that mindfulness may be an effective intervention for addressing externalizing behaviors and attentional problems among first-year college students.