OBJECTIVES Provision of reproductive health preventive services to adolescents is critical given their high rates of sexually transmitted infections and unintended pregnancies. Pediatricians are well positioned to provide these services but often face barriers. With this project, we aimed to build quality improvement (QI) capacity within pediatric practices to improve adherence to national guidelines for adolescent reproductive health preventive services. METHODS In 2016, an accountable care organization overseeing health care delivery for low-income children in the Midwestern United States used practice facilitation, a proven approach to improve health care quality, to support pediatric practices in implementing reproductive health QI projects. Interested practices pursued projects aimed at providing (1) sexual risk reduction and contraceptive counseling (reproductive health assessments [RHAs]) or (2) etonogestrel implants. QI specialists helped practices build key driver diagrams and implement interventions. Outcome measures included the proportion of well-care visits with RHAs completed and number of etonogestrel insertions performed monthly. RESULTS Between November 1, 2016, and December 31, 2019, 6 practices serving >7000 adolescents pursued QI projects. Among practices focused on RHAs, the proportion of well-care visits with completed RHAs per month increased from 0% to 65.8% (P < .001) within 18 months. Among practices focused on etonogestrel implant insertions, overall insertions per month increased from 0 to 8.5 (P < .001). CONCLUSIONS Practice facilitation is an effective way to increase adherence to national guidelines for adolescent reproductive health preventive services within primary care practices. Success was driven by practice-specific customization of interventions and ongoing, hands-on support.