Introduction: Emerging evidence supports an immunologic role for 25‐hydroxyvitamin D (25(OH)D) in inflammatory bowel disease (IBD). Here we examined if pretreatment vitamin D status influences durability of anti–tumor necrosis factor (TNF)–α therapy in patients with Crohn's disease (CD) or ulcerative colitis (UC). Methods: All IBD patients who had plasma 25(OH)D level checked <3 months prior to initiating anti–TNF‐α therapy were included in this retrospective single‐center cohort study. Our main predictor variable was insufficient plasma 25(OH)D (<30 ng/mL). Cox proportional hazards model adjusting for potential confounders was used to identify the independent effect of pretreatment vitamin D on biologic treatment cessation. Results: Our study included 101 IBD patients (74 CD; median disease duration 9 years). The median index 25(OH)D level was 27 ng/mL (interquartile range, 20–33 ng/mL). One‐third of the patients had prior exposure to anti–TNF‐α therapy. On multivariate analysis, patients with insufficient vitamin D demonstrated earlier cessation of anti–TNF‐α therapy (hazard ratio [HR], 2.13; 95% confidence interval [CI], 1.03–4.39; P = .04). This effect was significant in patients who stopped treatment for loss of response (HR, 3.49; 95% CI, 1.34–9.09) and stronger for CD (HR, 2.38; 95% CI, 0.95–5.99) than UC (P = NS). Conclusions: Our findings suggest that vitamin D levels may influence durability of anti–TNF‐α induction and maintenance therapy. Larger cohort studies and clinical trials of supplemental vitamin D use with disease activity as an end point may be warranted.