Objective: Dog owners have been shown to walk more per week compared to non-dog owners; however, 60% of dog owners are still not walking their dogs at intensities sufficient to reap optimal health benefits. The aim of this study was to evaluate the feasibility, acceptability, and efficacy of a 9-week feasibility randomized controlled trial involving a program of six weekly scheduled instructor-led group dog walks supplemented with theory-based strategies to encourage increased dog walking among dog owners in Greater Victoria, BC. Methods: This study was based on the multi-process action control (M-PAC) framework and utilized an open parallel randomized controlled trial design involving experimental and waitlist-control group participants. Quantitative data was collected using pedometers and self-report measures. A program evaluation survey was administered upon the completion of the study. Primary outcomes examined the feasibility and acceptability of the program; secondary outcomes analyzed pedometry and self-report moderate-to-vigorous physical activity (MVPA) data; and tertiary outcomes observed changes in participants’ perceptions of M-PAC constructs. Percentage calculations were used to obtain primary outcomes, and analysis of covariance (ANCOVA; controlling for baseline) was performed to examine secondary and tertiary outcomes to explore the direction of effects and obtain a first estimate of expected effect sizes. Eligibility: Male and female adults aged 18+ living in Greater Victoria, BC, who owned at least one healthy and friendly dog aged six months and above, who were not meeting recommended guidelines of 150 minutes of MVPA per week, and who were medically cleared to participate. Results: Feasibility outcomes included 74 interested responses, 23% recruitment rate (n = 17), 94% retention rate (n = 16), and 94% adherence rate (n = 15). Program participants were overall (very) satisfied with the program – worksheets (62.5%), program instructor (100%), various program/group dog walks logistics (75% to 100%). Total weekly step counts and average daily step counts, MVPA dog walking, and MVPA with dog increased at the end of the program and at follow-up, resulting in large effect sizes when compared to the waitlist-control group. MVPA dog walking and total MVPA (with and without dog) exceeded recommended guidelines at follow-up. Positive changes across time were observed for dog responsibility and M-PAC constructs of affective judgments, opportunity, planning, identity, and habit, resulting in medium and large effect sizes when compared to the waitlist-control group. Conclusions: This six-week group dog walking program is overall feasible, acceptable, and efficacious in encouraging increased dog walking and MVPA among dog owners. Attendance at weekly scheduled instructor-led group dog walks and exposure to the M-PAC construct worksheets resulted in program participants’ adoption and maintenance of positive behavioral changes at the end of the program and at follow- up. Program participants reported enjoying the program and being (very) satisfied with it. It is recommended for future studies to refine/modify initial recruitment strategies and eligibility criteria, reimburse medical/veterinarian clearance costs to reduce cost-related barriers to participation, offer a variety of options for program delivery (e.g., different locations/schedules/seasons, online programs, multi-site study) to accommodate more participants, and apply the M-PAC framework to a larger sample. / Graduate