To evaluate the impact of untreated deviated nasal septum (DNS) on recalcitrant chronic rhinosinusitis (CRS) among patients undergoing revision endoscopic sinus surgery (ESS). Case-control study. Tertiary academic center. We performed a retrospective review of 489 patients undergoing revision ESS for CRS at a tertiary academic center. Patients undergoing septoplasty were matched to nonseptoplasty controls based on age and sex. Preoperative Lund-Mackay score (LMS) was compared between cohorts. Linear regression was used to identify predictors of LMS and ostiomeatal complex (OMC) obstruction. Thirty-six matched pairs (72 patients) were selected for analysis: 36 undergoing septoplasty and revision ESS and 36 undergoing revision ESS alone. Compared with nonseptoplasty controls, the septoplasty group had a significantly higher average LMS (17.8 vs 14.6, P = .02) and a greater rate of OMC obstruction (89% vs 61%, P < .01). The septoplasty group also had significantly higher opacification scores in the maxillary (1.5 vs 1.2, P = .03) and posterior ethmoid (1.8 vs 1.4, P = .02) sinuses. On multivariable analysis, DNS was an independent predictor of LMS ( P = .02) and OMC obstruction ( P < .01). Untreated DNS is associated with radiographic markers of CRS severity among patients undergoing revision ESS and may contribute to the multifactorial pathogenesis of persistent CRS.