OBJECTIVE Fecal calprotectin (FC) has been suggested as a sensitive biomarker of inflammatory bowel disease (IBD). However, its usefulness in assessing IBD activity needs to be more precisely defined. In this meta-analysis we aimed to determine the diagnostic performance of FC in assessing IBD endoscopic activity in adults. METHODS We searched the databases PubMed/Medline and EMBASE, and studies which examined IBD endoscopic activity in association to FC were identified. From each study pooled data and consequently pooled sensitivity, specificity, likelihood ratios (LR), diagnostic odds ratios (DORs) and areas under the curve (AUCs) were calculated, using suitable meta-analysis software. We analyzed extracted data using fixed or random effects models, as appropriate, depending on the presence of significant heterogeneity. RESULTS We included 49 sets of data from 25 eligible for meta-analysis studies, with 298 controls and 2,822 IBD patients. Fecal calprotectin in IBD (Crohn's disease, CD and ulcerative colitis, UC) showed a pooled sensitivity of 85%, specificity of 75%, DOR of 16.3 and AUC of 0.88, in diagnosing active disease. The sub-group analysis revealed that FC performed better in UC than in CD (pooled sensitivity 87.3% vs 82.4%, specificity 77.1% vs 72.1% and AUC 0.91 vs 0.84). Examining the optimum FC cut-off levels, the best sensitivity (90.6%) was achieved at 50 μg/g, whereas the best specificity (78.2%) was found at levels >100 μg/g. CONCLUSIONS This meta-analysis showed that in adults, FC is a reliable laboratory test for assessing endoscopic activity in IBD. Its performance is better in UC than CD.