Background: Originally developed for resident self-assessment, the Plastic Surgery In-Service Examination has been administered for over 45 years. The Accreditation Council for Graduate Medical Education requires that at least 70 percent of graduates pass the American Board of Plastic Surgery Written Examination on their first attempt. This study evaluates the role of In-Service Exam scores in predicting Written Exam success. Methods: In-Service Exam scores from 2009 to 2015 were collected from the National Board of Medical Examiners. Data included residency training track, training year, and examination year. Written Exam data were gathered from the American Board of Plastic Surgery. Multivariate analysis was performed and receiver operating characteristic curves were used to identify optimal In-Service Exam score cut-points for Written Exam success. Results: Data from 1364 residents were included. Residents who failed the Written Exam had significantly lower In-Service Exam scores than those who passed (p < 0.001). Independent residents were 7.0 times more likely to fail compared with integrated/combined residents (p < 0.001). Residents who scored above the optimal cut-points were significantly more likely to pass the Written Exam. The optimal cut-point score for independent residents was the thirty-sixth percentile and the twenty-second percentile for integrated/combined residents. Conclusions: Plastic Surgery In-Service Exam scores can predict success on the American Board of Plastic Surgery Written Exam. Residents who score below the cut-points are at an increased risk of failing. These data can help identify residents at risk for early intervention.