ObjectiveTo compare fiber‐optic nasal endoscopy with Müller’s maneuver (FNMM) against drug‐induced sleep endoscopy (DISE) in diagnosing the presence of severe level‐specific upper airway collapse in patients with obstructive sleep apnea/hypopnea syndrome (OSAHS).Study DesignCase series with chart review.SettingTertiary care academic center.Subjects and MethodsMedical records of all adult patients undergoing diagnostic DISE as part of their surgical evaluation were reviewed. Patients were included if they had undergone FNMM and had documented Friedman tongue position and tonsillar grade prior to DISE. Airway obstruction on both endoscopic procedures was described according to airway level and severity. Severe airway obstruction was defined as >75% collapse on endoscopy.ResultsFifty‐three patients were included in this study. Fiber‐optic nasal endoscopy with Müller’s maneuver and DISE did not differ significantly regarding the presence of severe retropalatal airway collapse. There was a statistically significant difference in the incidence of severe retrolingual collapse identified via DISE (84.9% [45/53]) compared with FNMM (35.8% [19/53]; P <. 0001). This discrepancy between FNMM and DISE findings was statistically significant in individuals with Friedman I and II tongue positions (FNMM = 16.7%, DISE = 88.9%, P <. 0001) and individuals with Friedman III tongue position (FNMM = 31.8%, DISE = 81.8%, P =. 002). Patients with Friedman IV showed no significant difference (P =. 65) between FNMM (69.2%) and DISE (84.6%).ConclusionThis study shows a significant difference between FNMM and DISE in the identification of severe retrolingual collapse. Since the effectiveness of surgical interventions depends largely on the accurate preoperative identification of the site of obstruction, further scrutiny of each diagnostic endoscopic technique is warranted.