<p>Mindfulness-based interventions have been shown to be mild to moderately effective at decreasing the stress of parents raising children with behavior difficulties. However, questions surround whether mindfulness practices cause changes in specific mindfulness processes—present-moment awareness and responding with acceptance—and how these changes relate to decreased stress. This single-case design pilot study examined how practicing a daily mindfulness exercise affected parents’ mindfulness processes, stress, and happiness over time. Participants were four parents with clinically elevated levels of stress who had a child experiencing clinical levels of behavior problems. Each participated in a non-intervention baseline phase and then was introduced to an audio-recorded mindful breathing exercise. In the intervention phase, participants were asked to complete the mindful breathing exercise twice a day for 14 days. Across phases, participants completed daily single-item ratings of mindfulness processes (i.e., awareness and acceptance) and stress as well as weekly probes of mindfulness and stress using multi-item rating scales. Results showed that practicing the mindfulness exercise had a functional relationship with gradual improvements in participants’ awareness, stress, and happiness; however, a functional relationship was not supported between practicing the mindfulness exercise and changes in acceptance. We conclude that practicing mindful breathing consistently through small and simple daily exercises appears beneficial for improving some aspects of mindfulness and decreasing stress for parents with children demonstrating significant behavioral problems. Changes in mindfulness and desired outcomes may depend, in part, on the consistency with which specific mindfulness processes are practiced. Recommendations for future research and practice are discussed.</p>