Background: Despite recent advances in acute stroke intervention, secondary prevention strategies are lacking. Physical activity (PA) is the second-largest predictor of stroke and a cornerstone of secondary prevention therapies. Interventions to promote PA post-stroke include components aimed at reducing sedentary behaviour and increasing participation in lifestyle PA and structured exercise. Despite guidelines to adapt PA to individuals’ needs, there is no evidence on the empirical development of adaptive PA interventions post-stroke. This study will explore patient, caregiver and multidisciplinary healthcare professional perspectives on the design and delivery of adaptive, personalised PA interventions, delivered using a smartphone application, following mild-to-moderate stroke. Findings will directly inform the protocol of an experimental trial, using a novel adaptive trial design. Methods: A descriptive qualitative study will be undertaken to inform the design, delivery and subsequent acceptability of a smartphone application to reduce sedentary behaviour and promote PA post-stroke. Data will be collected via one-to-one interviews and focus groups and analysed according to a six-step thematic analysis. Findings will be reported in accordance with the consolidated criteria for reporting qualitative research (COREQ) checklist. One-to-one interviews and focus group interviews will be conducted with three stakeholder groups: 1) People post-stroke, who are independently mobile, without communication and cognitive deficits, living in the community, and without other diagnosed neurological conditions. 2) Caregivers (formal and informal) involved in post-stroke care. 3) Healthcare professionals who are members of multidisciplinary stroke teams. Ethics and dissemination: Ethical approval has been granted by the Faculty of Education and Health Sciences Research Ethics Committee at the University of Limerick [Ref: 2019_10_03_ EHS]. Findings will be shared locally with all stakeholder groups, submitted for publication, and will inform the protocol and conduct for a novel and flexible experimental trial, examining the effectiveness of an adaptive PA intervention post-stroke.