Background: Vitamin D deficiency is highly prevalent among patients with IBD, however, data on its association with clinical outcomes are conflicting. Aim: To perform a systematic review and meta-analysis to explore the association of low vitamin D status with clinical outcomes in patients with IBD. Methods: We searched PubMed, Embase, Scopus and Web of Science from inception to February 2018 for observational studies evaluating the association of low 25(OH)D status on IBD disease activity, mucosal inflammation, clinical relapse and quality of life. Odds ratios (ORs) were pooled and analysed using a random effects model. Results: Twenty-seven studies were eligible for inclusion comprising 8316 IBD patients (3115 ulcerative colitis, 5201 Crohn's disease). Among IBD patients, low 25(OH)D status was associated with increased odds of disease activity (OR 1.53, 95% CI 1.32-1.77, I² = 0%), mucosal inflammation (OR 1.25, 95% CI 1.06-1.47, I² = 0%), low quality of life (QOL) scores (OR 1.30, 95% CI 1.06-1.60, I² = 0%) and future clinical relapse (OR 1.23, 95% CI 1.03-1.47, I² = 0%). In subgroup analysis, low vitamin D status was associated with Crohn's disease activity (OR 1.66, 95% CI 1.36-2.03, I² = 0%), mucosal inflammation (OR 1.39, 95% CI 1.03-1.85, I² = 0%), clinical relapse (OR 1.35, 95% CI 1.14-1.59, I² = 0%), and low QOL scores (OR 1.25, 95% CI 1.04-1.50, I² = 0%) and ulcerative colitis disease activity (OR 1.47, 95% CI 1.03-2.09, I² = 0%) and clinical relapse (OR 1.20, 95% 1.01-1.43, I² = 0%). Conclusions: Low 25(OH)D status is a biomarker for disease activity and predictor of poor clinical outcomes in IBD patients.