Gastrointestinal (GI) diseases are highly prevalent worldwide, with considerable morbidity and mortality. Curcumin has been used for many years as a plant-derived product for the management of various conditions such as abdominal pain and poor digestion. This systematic review was undertaken with the aim of investigating the effect of curcumin or turmeric supplementation on GI diseases. A comprehensive systematic search was conducted in PubMed, Scopus, Web of Science and Google Scholar up to March 2020 to identify clinical trials assessing the effect of curcumin/turmeric alone or in combination with other herbs or nutrients on GI diseases. Twenty-one studies comprising 1478 GI patients were included in the study. Four out of seven studies showed a beneficial effect of curcumin/turmeric supplementation on irritable bowel syndrome (IBS) and six out of seven showed positive effects of these herbs on ulcerative colitis. Two out of four studies highlighted the potential role of curcumin/turmeric in eradication of H. pylori infection. Both studies conducted on peptic ulcer disease and two out of four studies performed on Crohn's disease demonstrated positive effects of curcumin/turmeric supplementation. One study showed curcumin supplementation had no effect on familial adenomatous polyposis. However, in another study, curcumin had favorable effects on proctosigmoiditis. Nine studies reported some minor adverse effects. The results of this systematic review suggest a beneficial effect of curcumin/turmeric supplementation on the management of GI diseases. More randomized clinical controlled trials are needed to confirm these results.