Close social relationships, especially within couples, influence health habits, including physical activity and exercise (PA/EX) behaviors, in both positive and negative ways depending on the quality of the relationship and partner support. Among older adult couples, the influence of PA/EX support on PA/EX habits has been incompletely characterized and could benefit from research that a) intentionally includes both halves of dyads, b) is anchored by an interpersonal health behavior theoretical framework, and c) utilizes a mixed-methods research MMR approach. The overarching objective of this two-phase dissertation project was to 1) capture dyadic patterns of PA/EX behaviors and support, and 2) assess the effects of support behaviors on PA/EX habits in older adult couples. Phase One (8 older adult couples) utilized a MMR approach and measured objective PA via accelerometers and social support and relationship quality outcomes via validated questionnaires. Semi-structured interviews allowed themes to be detected. Phase Two utilized an online survey battery to assess similar outcomes in 47 older adult couples. Primary results from Phase One indicated that the qualitative analysis further advanced understanding of dyadic PA/EX participation and PA/EX partner support with the themes of tangible supportive inaction and non-tangible supportive perceptions and provided further support for use of the Positive and Negative Social Control Scales. In Phase Two, our most notable finding was that within this sample of older couples, a partner’s PA/EX support perceptions influenced their partners’ PA/EX participation, and, a partner’s PA/EX influenced their partners’ perceptions of PA/EX support. This finding aligns with PA/EX support dynamics noted in Phase One. That is, for some partners, they felt PA/EX support from their partners when their partners were engaging in PA/EX with them. This concept supports the potential bidirectional influence in our findings by introducing the possibility of shared PA/EX as a mediator of the dyadic bidirectional influence of PA/EX partner support and PA/EX participation. More research is needed in this emergent area. Application of this data may inform the design of effective PA/EX programs that leverage social support to enhance adherence to PA/EX guidelines for older adults, a key health behavior for successful aging.INDEX WORDS: Older adults, dyadic influence, Physical Activity, Partner Support, Mixed-Methods Research, Actor-Partner Interdependence Model