OBJECTIVE To determine whether social media, specifically Facebook, is an effective tool for improving contraceptive knowledge. METHODS English-speaking women aged 18-45 years receiving care at an urban academic center obstetrics and gynecology clinic were included and randomized to a trial of standard contraceptive education and pamphlet (n=74) compared with standard contraceptive education and Facebook (n=69) information for contraception counseling. Contraceptive knowledge was evaluated preintervention and postintervention by the Contraceptive Knowledge Inventory. We evaluated the effect of the intervention by raw score and percent increase in Contraceptive Knowledge Inventory score, participant satisfaction with counseling method, and contraceptive preference postintervention. All analyses were stratified by age group. RESULTS The median raw postintervention Contraceptive Knowledge Inventory score was significantly higher in the Facebook compared with the pamphlet group (15 compared with 12, P<.001) as was percentage increase in the Contraceptive Knowledge Inventory score (36% compared with 12%, P<.001). Participant satisfaction with counseling method was significantly higher in the Facebook group (median 10 compared with 6, P<.001). Participant contraceptive preference for long-acting reversible contraceptives (LARCs; intrauterine device or implant) postintervention was significantly greater in the Facebook compared with the pamphlet group (57% compared with 35%, P=.01). Among women currently using none or barrier contraception, contraceptive preference for implants was significantly greater in the Facebook compared with the pamphlet group (26% compared with 5%, P=.02), although, when analysis was extended to include implant or intrauterine device, LARCs were not significantly higher in the Facebook compared with the pamphlet group (48% compared with 33%, P=.19). CONCLUSION Social media as an adjunct to traditional in-office counseling improves patient contraceptive knowledge and increases patient preference for LARCs. CLINICAL TRIAL REGISTRATION ClinicalTrials.gov, www.clinicaltrials.gov, NCT5327714500.