Objective: This study examined rumination as a mediator of the relationship between dispositional mindfulness (DM) and depression, loneliness, and anxiety, while considering gender as a moderator of these mediation models. Participants: Three hundred and nineteen undergraduate students (49.5% female; M=18.90years) participated with data collected from January 2018 to April 2019. Methods: Self-report measures of DM, rumination, symptoms of anxiety and depression, loneliness, and social support were completed. Results: Males scored significantly higher than females on DM, while females scored significantly higher than males on rumination and psychological distress. Rumination mediated the relationship between DM and all adjustment variables. The mediation model predicting depression was moderated by gender, showing stronger effects for females than males. Conclusion: Results support rumination as a mechanism underlying the association between DM and psychological adjustment and suggest that targeting both DM and rumination could maximize the effectiveness of mindfulness-based interventions for college students' well-being.