Background Combined Internal Medicine/Pediatrics (Med/Peds) residencies rely on categorical program data to predict pass rates for the American Board of Internal Medicine Certifying Exam (ABIM-CE) and the American Board of Pediatrics Certifying Exam (ABP-CE). There is insufficient literature describing what best predicts a Med/Peds resident passing board exams. In this study, we aimed to determine how standardized test scores predict performance on ABIM-CE and ABP-CE for Med/Peds residents. Methodology We analyzed prior exam scores for 91/96 (95%) residents in a Med/Peds program from 2008 to 2017. Scores from the United States Medical Licensing Examination (USMLE) Steps 1 and 2 Clinical Knowledge (CK) and In-Training Exams in Internal Medicine (ITE-IM) and Pediatrics (ITE-P) were analyzed with the corresponding ABIM-CE and ABP-CE first-time scores. Linear and logistic regression were applied to predict board scores/passage. Results USMLE 1 and 2 CK, ITE-IM, and ITE-P scores had a linear relationship with both ABIM-CE and ABP-CE scores. In the linear regression, adjusted R 2 values showed low-to-moderate predictive ability (R 2 = 0.11-0.35), with the highest predictor of ABIM-CE and ABP-CE being USMLE Step 1 (0.35) and Postgraduate Year 1 (PGY-1) ITE-IM (0.33), respectively. Logistic regression showed odds ratios of passing board certifications ranging from 1.05 to 1.53 per point increase on the prior exam score. The PGY-3 ITE-IM was the best predictor of passing both certifying exams. Conclusions In one Med/Peds program, USMLE Steps 1 and 2 and all ITE-IM and ITE-P scores predicted certifying exam scores and passage. This provides Med/Peds-specific data to allow individualized resident counseling and guide programmatic improvements targeted to board performance.