Bereavement is one of the most common and stressful human experiences, affecting nearly 8 million people per year in the United States. Following loss, yearning and rumination are repetitive thought processes that increase the risk for poor grief outcomes. Mindfulness Meditation (MM) training has been found to reduce unhelpful repetitive thought processes. However, research on MM training in bereaved populations is limited. The present study is a novel randomized controlled trial of a 6-week MM training for widows and widowers. We hypothesize that participants in the MM training will have better grief outcomes compared to participants in a 6-week progressive muscle relaxation training or waitlist condition. In addition, we hypothesize the MM training will improve grief outcomes by reducing yearning and rumination. This study is novel in its rigorous examination of the process by which MM training may improve grief outcomes through the reduction of repetitive thought processes in a bereaved population. Findings from the present study will advance scientific knowledge of intervention for bereavement and, more broadly, potential mechanisms of change for maintenance of mental and physical health following profound life stress.