This secondary analysis examined changes in sleep quality associated with participation in a Mindfulness-Based Stress Reduction (MBSR) program among healthy older adults. Data were collected at baseline, 8-weeks post-treatment, and a 6-month follow-up from adults aged ≥ 65 (N = 200), randomly assigned to MBSR or a waitlist control. Group differences were examined using mixed analysis of covariance with repeated measures on the total Pittsburgh Sleep Quality Index (PSQI) score. A small-sized, significant effect was found on overall sleep among MBSR participants with baseline PSQI scores > 5, indicative of a sleep disturbance, F(2, 80) = 4.32, p = .02, _p² = .05. A medium-sized, significant effect was found for MBSR participants with baseline PSQI scores ≥ 10, F(2, 28) = 3.13, p = .04, _p² = .10. These findings indicate that improved sleep quality for older adults who have higher levels of sleep disturbance may be associated with participation in MBSR.