Background: Intraoperative visualization of cerebrospinal fluid (CSF) during endoscopic endonasal resection of skull base tumors is the most common factor contributing to the development of postoperative CSF leaks. No previous studies have solely evaluated preoperative factors contributing to intraoperative CSF visualization. The purpose of this study was to identify preoperative factors predictive of intraoperative CSF visualization. Methods: Retrospective review of patients who underwent transsphenoidal resection of pituitary adenomas was conducted. Clinical and radiographic variables were compared for those who had CSF visualized to those who did not. Nominal logistic regression models were built to determine predictive variables. Results: Two hundred and sixty patients were included in the study. All significant demographic and radiographic variables on univariate analysis were included in multivariate analysis. Two multivariate models were built, as tumor height and supraclinoid extension were collinear. The first model, which considered tumor height, found that extension into the third ventricle carried a 4.60-fold greater risk of CSF visualization (P = 0.005). Increasing tumor height showed a stepwise, linear increase in risk; tumors >3 cm carried a 19.02-fold greater risk of CSF visualization (P = 0.003). The second model, which considered supraclinoid tumor extension, demonstrated that extension into the third ventricle carried a 4.38-fold increase in risk for CSF visualization (P = 0.010). Supraclinoid extension showed a stepwise, linear increase in intraoperative CSF risk; tumors with >2 cm of extension carried a 9.26-fold increase in risk (P = 0.017). Conclusion: Our findings demonstrate that tumor height, extension into the third ventricle, and extension above the clinoids are predictive of intraoperative CSF visualization.