A number of studies have investigated the impact of mindfulness-based interventions on symptoms of post-traumatic stress (PTSD) compared to control conditions. The current meta-analysis consolidated findings from 18 studies reporting results for 21 samples of participants. Across studies, mindfulness-based treatments compared to control conditions were effective in ameliorating symptoms of PTSD, with Hedges' g=-0.44. Hedges' g was -0.59 for comparison of mindfulness-based interventions to waitlist control conditions. Changes in mindfulness may underpin the effect of mindfulness-based interventions on PTSD symptoms and thus the meta-analysis examined findings regarding increases in mindfulness. The 12 studies that assessed mindfulness found that the interventions significantly increased mindfulness, Hedges' g=0.52. Moderator analyses indicated that interventions with longer mindfulness training were more efficacious in reducing symptoms of PTSD. Across studies, gender, age, veteran status, or length of time between the intervention and assessment of PTSD symptoms did not moderate the impact of mindfulness-based interventions. The results provide a foundation for future research directions and have implications for work with those impacted by trauma.