Aggression by individuals with developmental disabilities may threaten their community placement. In a multiple baseline design across group homes, we provided group home staff with behavioral training and later with mindfulness training to assess the impact on aggressive behaviors and the number of learning objectives mastered by individuals in their care. We also assessed other outcomes including activities engaged in by the individuals, use of restraint by staff, and measures of satisfaction. The effect of varying staff-resident ratios was evaluated on all measures. When compared to baseline, the number of staff interventions for aggression showed some reduction following behavioral training, but decreased substantially only following mindfulness training. There was also some increase in the number of learning objectives mastered by the individuals following behavioral training, but greater and more consistent increases were obtained only after mindfulness training. Improvements also occurred on the other measures assessed after behavioral training, but these were always greater and more consistent following mindfulness training. In addition, consistent gains followed behavioral training only with a high staff-resident ratio whereas the larger gains after mindfulness training occurred with both medium and low staff-resident ratios. Our results suggest that the addition of mindfulness training considerably enhanced the ability of the group home staff to effectively manage the aggressive behavior and learning of the individuals.