Objective: The pedicled nasoseptal flap (NSF) is the widely accepted reconstructive technique of choice for repair of larger skull base defects after endoscopic endonasal approaches. There is a dearth of literature examining the decision-making process regarding flap harvest. The objective of this study is to evaluate preoperative characteristics that predict the use of NSF reconstruction after endoscopic transsphenoidal resection of pituitary tumors. Methods: In this retrospective case control study, demographic, clinical, imaging, and procedural details were gathered on all patients undergoing endoscopic transsphenoidal pituitary adenoma resection at a single academic center since January 2009. Characteristics were compared for patients receiving an NSF and those not undergoing NSF repair. A multivariate model that best predicted the use of an NSF was built and a risk score was developed. Results: Two hundred thirty-eight patients were included, and 39 underwent NSF placement. Tumor size and anatomic characteristics were the predominant factors that significantly differed between cases and controls. Patients with transsellar tumor extension had 6.3 higher odds of requiring NSF, each millimeter increase in tumor height on coronal T1 magnetic resonance imaging increased the odds of NSF use by 1.2. The flap risk score (FRS) is calculated by adding tumor height (mm) to 6 if there is transsellar extension. At an FRS of >35, the FRS is 87% specific and 85% sensitive for flap placement. Conclusions: Preoperative imaging characteristics can predict NSF use. The FRS can be applied by surgical teams and referring physicians to determine which patients are more likely to undergo NSF repair.