Physical activity provides numerous health benefits. However, many individuals are chronically underactive and have difficulty maintaining regular physical activity. Physical activity interventions may benefit from integrative, experimental approaches based in neurobiological models of behavior that also combine mind-body techniques such as mindfulness and guided imagery. Mindfulness is evidenced to amplify self-regulatory ability and guided imagery is shown to have a positive influence on goal-setting and physical activity motivations. This 2-phase study includes an initial development process to create brief (~4 minutes) mindfulness informed physical activity based guided imagery audio files that target distinct cognitive and affective processes that underly neurobiological models of behavior. In the second phase, participants completed a 2-week pilot intervention study to gather qualitative and quantitative data on intervention feasibility and acceptability. Results indicate that participants found the mindfulness informed guided imagery to be easy to use, enjoyable and helpful. Over a two-week intervention period participants reported positive shifts in behavior change, physical activity enjoyment, increased mindfulness during physical activity, and increased physical activity self-efficacy and satisfaction. Interview data revealed that participants increased their frequency of physical activity and tended to experience positive affect during physical activity, engaged in future oriented thinking and were able to view physical activity in a more positive light. This study extends health behavior change intervention research and provides supporting evidence for a flexible and tailorable online mindfulness-based intervention.