Purpose: There is a need to improve delivery of family planning services, including preconception and contraception services, in primary care. We assessed whether a clinician-facing clinical decision support implemented in a family medicine staffed primary care network improved provision of family planning services for reproductive-aged female patients, and differed in effect for certain patients or clinical settings. Methods: We conducted a pragmatic study with difference-in-differences design to estimate, at the visit-level, the clinical decision support's effect on documenting the provision of family planning services 52 weeks prior to and after implementation. We also used logistic regression with a sample subset to evaluate intervention effect on the patient-level. Results: 27,817 eligible patients made 91,185 visits during the study period. Overall, unadjusted documentation of family planning services increased by 2.7 percentage points (55.7% pre-intervention to 58.4% intervention). In the adjusted analysis, documentation increased by 3.4 percentage points (95% CI: 2.24, 4.63). The intervention effect varied across sites at the visit-level, ranging from a -1.2 to +6.5 percentage point change. Modification of effect by race, insurance, and site were substantial, but not by age group nor ethnicity. Additionally, patient-level subset analysis showed that those exposed to the intervention had 1.26 times the odds of having family planning services documented after implementation compared to controls (95% CI: 1.17, 1.36). Conclusions: This clinical decision support modestly improved documentation of family planning services in our primary care network; effect varied across sites. (C) 2019 Elsevier Inc. All rights reserved.