Background Middle childhood (ages 8-12 years) is a critical period for forming behavioral habits and reducing the risk for the development of skin cancer later in life. During this time, children develop more autonomy and spend more unsupervised time away from their parents. Professional agencies recommend that all children engage in regular sun protection behaviors and avoid the sun during peak daytime hours. Unfortunately, in middle childhood, child sun protection often declines and UV radiation exposure increases. Effective parenting involves balancing ways to encourage the child’s increasing independence while providing practical assistance to ensure sun protection is implemented. Objective The goal was to evaluate the feasibility, acceptability, and preliminary effects of Sun Safe Families, a Facebook group intervention for parents of children between 8 and 12 years of age. Methods The team developed Facebook messages targeting parent knowledge, normative influences, sun safety barriers, planning and goal setting, confidence in implementing sun safety, communication, forming habits, and managing sun safety in risky situations. A total of 92 parents were enrolled, and the groups ran for 6 weeks. Feasibility was measured by enrollment and retention rates. Acceptability was measured by engagement in the Facebook groups. Satisfaction was assessed by a treatment evaluation. At pre- and post-intervention, parents completed measures of child sun protection, UV radiation exposure, sunburn, sun safety knowledge, child risk, barriers, sun protection self-efficacy, planning, sun safe habits, norms for child sun safety, and communication about sun safety. Results Enrollment (64.3%, 92/143) and retention (94.6%, 87/92) were good. On average, participants viewed 67.6% (56.8/84) of posts, “liked” 16.4% (13.77/84) of posts, commented on 14.8% (12.43/84) of posts, and voted on 46% (6.4/14) of polls. Satisfaction was excellent. From pre- to post-intervention, there were significant increases in child sun protection, sun exposure, and sunburn (P<.01; moderate effect sizes), as well as statistically significant increases in planning and self-efficacy (P<.05) and family norms and parent communication (P<.01). Conclusions This study demonstrated high survey retention, acceptability, and satisfaction with the intervention. There were promising preliminary effects on child sun protection behaviors and parent sun protection attitudes and communication with their child. Replication with a larger sample size and a comparison condition is warranted.