Background: The use of intestinal ultrasound (IUS) in the management of inflammatory bowel disease (IBD) is emerging. We aim to determine the performance of IUS in the assessment of disease activity in IBD. Methods: This is a prospective cross-sectional study of IUS performed on IBD patients in a tertiary centre. IUS parameters including intestinal wall thickness, loss of wall stratification, mesenteric fibrofatty proliferation, and increased vascularity were compared with endoscopic and clinical activity indices. Results: Among the 51 patients, 58.8% were male, with a mean age of 41 years. Fifty-seven percent had underlying ulcerative colitis with mean disease duration of 8.4 years. Against ileocolonoscopy, IUS had a sensitivity of 67% (95% confidence interval (CI): 41-86) for detecting endoscopically active disease. It had high specificity of 97% (95% CI: 82-99) with positive and negative predictive values of 92% and 84%, respectively. Against clinical activity index, IUS had a sensitivity of 70% (95% CI: 35-92) and specificity of 85% (95% CI: 70-94) for detecting moderate to severe disease. Among individual IUS parameters, presence of bowel wall thickening (>3 mm) had the highest sensitivity (72%) for detecting endoscopically active disease. For per-bowel segment analysis, IUS (bowel wall thickening) was able to achieve 100% sensitivity and 95% specificity when examining the transverse colon. Conclusions: IUS has moderate sensitivity with excellent specificity in detecting active disease in IBD. IUS is most sensitive in detecting a disease at transverse colon. IUS can be employed as an adjunct in the assessment of IBD.