Background: Parents play a major role in supporting physical activity in and around the home, creating a home environment that encourages physical activity as well as participation in activity with their children and supporting children's physically active lifestyles are important areas of concern for health promotion. Despite support for family-based interventions, there is still little evidence to demonstrate the most effective ways of targeting families with physical activity interventions. Social media has been one area of promise for connecting with parent participants in physical activity interventions. Sites like Facebook have an existing high prevalence of parent users and offer media-rich tools in a socially connected digital environment that are suited for connecting with parents. The purpose of this study was to determine if the use of a social media physical activity intervention could enhance physical activity behavior change in parents. Additionally, this study sought to discover if the level of parent engagement in the social media group influenced their behavior change-related outcomes, within the same intervention. Methods: Parent participants in this study were randomized at the school level as part of a larger physical activity intervention consisting of three different experimental conditions (Control, School, Family). Participants in the family intervention received a nineteen-week strategic messaging campaign delivered through a Facebook group in addition to existing family intervention components. Strategic messaging consisted of core messaging related to parent education as well as dedicated behavior change messaging targeting parents specific to their existing stage of change. Parent completed pre/post survey instruments to evaluate family health behaviors ((Family Health Climate (FHC), Stage of Change (SOC), Parent Support for Physical Activity (PSPA) and Physical Activity (PA) levels) and attitudes in an existing family-based physical activity intervention. Additional data were collected on interaction in the Facebook group to determine parents engagement level with Facebook content. Results: A total of 84 parents were included in the analysis control n = 42 and family n = 42. A repeated measures MANOVA was used to determine if there were significant differences between groups by time. Overall Pillai's trace was statistically significant for time*group F (8, 75) = 2.866, p = .008, partial η 2 = .234. Follow-up univariate ANOVA's were performed to determine which of the study variables across time points had significant mean differences, Family health climate p < .02, parent support p < .004, self-efficacy p < .034 all had significant mean differences between times and groups. No other study variables were significantly different. Pairwise comparisons showed significant mean improvements for family intervention participants in Family health climate (m = 4.972, p < .017) and parent support (m = 7.69, p < .005). Conclusion: Results indicate that strategic messaging campaigns delivered thro...