BACKGROUND:The prevalence of social media makes it a potential alternative to traditional offline methods of recruiting and engaging participants in health research. Despite burgeoning use and interest, few studies have rigorously evaluated its effectiveness and feasibility in terms of recruitment rates and costs, sample representativeness, and retention. OBJECTIVE:This study aimed to determine the feasibility of using Facebook to recruit employed Australian parents to an online survey about managing work and family demands, specifically to examine (1) recruitment rates and costs; (2) sample representativeness, compared with a population-based cohort of parents; and (3) retention, including demographic and health characteristics of parents who returned to complete a follow-up survey 6 weeks later. METHODS:Recruitment was conducted using 20 paid Facebook advertising campaigns, supplemented with free advertising approaches such as posts on relevant Facebook pages and requests for professional networks to circulate the survey link via Facebook. Recruitment rates and costs were evaluated using the Checklist for Reporting Results of Internet E-Surveys, including view rate, participation rate, completion rate, cost per consent, and cost per completer. Sample representativeness was evaluated by comparing demographic and outcome variables with a comparable sample from the Longitudinal Study of Australian Children including educational attainment, marital status, country of birth, neighborhood disadvantage, work-family conflict, and psychological distress. Retention was evaluated by comparing the number and demographic characteristics of participants at recruitment and at 6-week follow-up. RESULTS:Recruitment strategies together resulted in 6653 clicks on the survey link, from which 5378 parents consented to participate and 4665 (86.74%) completed the survey. Of those who completed the survey, 85.94% (4009/4665) agreed to be recontacted, with 57.79% (2317/4009) completing the follow-up survey (ie, 43.08% [2317/5378] of parents who consented to the initial survey). Paid Facebook advertising recruited nearly 75% of the sample at Aus $2.32 per completed survey (Aus $7969 spent, 3440 surveys completed). Compared with a population-based sample, participants at baseline were more likely to be university educated (P<.001), experience greater work-family conflict (P<.001) and psychological distress (P<.001), and were less likely to be born outside Australia (P<.001) or live in a disadvantaged neighborhood (P<.001). CONCLUSIONS:Facebook provided a feasible, rapid method to recruit a large national sample of parents for health research. However, some sample biases were observed and should be considered when recruiting participants via Facebook. Retention of participants at 6- to 8-week follow-up was less than half the initial sample; this may reflect limited ongoing participant engagement for those recruited through social media, compared with face-to-face.