Happiness is a critical indicator of quality of life in humans. A few studies have measured levels of happiness displayed under different conditions by individuals with profound multiple disabilities. We were interested in determining whether increasing the mindfulness of caregivers would result in increased levels of happiness in adults with these conditions. Using alternating treatments embedded within a multiple baseline across caregivers design, we measured baseline levels of happiness displayed by three adults with profound multiple disabilities when they engaged in leisure activities, each by a different pair of caregivers. Then, we taught mindfulness methods to one of each pair and measured the levels of happiness displayed by the individuals during the 8-weeks training for the caregivers. Finally, we measured the levels of happiness displayed by the three individuals for 16 weeks following the termination of mindfulness training. We found that, regardless of whether the level of happiness was initially observed to be high or low in the presence of a caregiver, it increased markedly when an individual interacted with a caregiver who received training in mindfulness when compared to the control caregiver, who did not receive such training. Our study provides evidence that increasing the mindfulness of a caregiver can produce a substantial increase in the levels of happiness displayed by individuals with profound multiple disabilities.