People with multiple sclerosis (PwMS) report greater emotion dysregulation, which is associated with increased symptoms of depression and anxiety, and reduced quality of life. Given the transdiagnostic significance of emotion dysregulation, the current study was designed to assess the feasibility and treatment effects of mindfulness meditation in reducing emotion dysregulation for PwMS. Method: Sixty-one PwMS were randomized to 1 of 3 groups: 4-week mindfulness-based training (MBT), 4-week adaptive cognitive training (aCT), or a waitlist control group. Using self-report and behavioral measures, we examined the effects of MBT on emotion dysregulation, use of emotion regulation strategies, experience of negative and positive affect, and overall quality of life. Results: Mindfulness training was associated with reduced emotion dysregulation compared with the adaptive cognitive training and the waitlist control group ( p 2 ϭ .20). Relative to the waitlist group, the MBT group also demonstrated reductions on a composite score of preservative cognition, measuring rumination and worry ( p 2 ϭ .15). However, there was no differential use of emotion regulation strategies or between-groups differences in overall quality of life as a function of training. Conclusions: Our pilot study provides preliminary support for MBT to reduce self-reported emotion dysregulation in PwMS. Given the widespread prevalence of mental health disturbances in this population, MBT can serve as a promising rehabilitation tool for PwMS (clinicaltrials.gov # NCT02717429). Impact and ImplicationsThis pilot RCT provides support for a brief, 4-week, mindfulness-based training to reduce emotion dysregulation in individuals with multiple sclerosis (MS). This study makes a significant contribution to the literature by comparing mindfulness training to an active control group, matching important intervention components, including group-based format, facilitator contact, and homework assignments, and implementing strategic recruitment efforts to minimize demand characteristics. Critically, MS-related declines in physical and cognitive functioning may serve as barriers to other potential psychosocial interventions targeting emotion dysregulation, thus making this brief, group-based, mindfulness training an ideal candidate for improving psychosocial wellness in those with MS.