Lactobacillus reuteri DSM 17938 has been one of the most extensively studied probiotic in children and adults with functional gastrointestinal disorders. In order to gather evidence on the efficacy of Lactobacillus reuteri DSM 17938 for treating and preventing some of these disorders. MEDLINE and the Cochrane Library were searched till February 2018 for relevant randomized controlled trials, retrospective studies, and meta-analyses with no language restrictions. The recent probiotic literature strongly suggests that Lactobacillus reuteri may be effective in the prevention and treatment of certain clinical conditions, such as infantile colic, infantile regurgitation, functional constipation, acute gastroenteritis, acute diarrhea, antibiotic-associated diarrhea, and necrotizing enterocolitis. No safety concerns with regard to the use of Lactobacillus reuteri in non-immunocompromised subjects were identified. A recent meta-analysis also supports the safety of using Lactobacillus reuteri even in preterm infants. This review presents the history of Lactobacillus reuteri DSM 17938 and the evidence base for its application in the health and disease.