Objective:A randomized, double‐blind, placebo‐controlled multicenter study to evaluate efficacy and safety of a mixture of non‐digestible carbohydrates (NDC) as an adjunct to oral rehydration therapy in treatment of acute infectious diarrhea in children with mild to moderate dehydration.Methods:144 boys aged 1 to 36 months with diarrhea defined as three or more watery stools per day for >1 day but <5 days with mild or moderate dehydration (World Health Organization criteria) were randomly assigned to receive hypotonic oral rehydration solution (ORS) (Na 60 mmol/L, glucose 111 mmol/L) with or without a mixture of NDC (soy polysaccharide 25%, α‐cellulose 9%, gum arabic 19%, fructooligosaccharides 18.5%, inulin 21.5%, resistant starch 7%).Results:Intention‐to‐treat analysis did not show significant differences in mean 48 hour stool volume (ESPGHAN‐ORS with NDC versus ESPGHAN‐ORS, 140 ± 124 g/kg versus 143 ± 114 g/kg; P = 0.41). Duration of diarrhea after randomization was similar in both groups (82 ± 39 hours versus 97 ± 76 hours, P = 0.24). There were no significant differences in the duration of hospital stay (111 ± 44 hours versus 126 ± 78 hours; P = 0.3). Unscheduled intravenous rehydration was similar in both groups (21.4% versus 16.2%, P = 0.42).Conclusion:In boys with acute non‐cholera diarrhea with mild to moderate dehydration a mixture of non‐digestible carbohydrates was ineffective as an adjunct to oral rehydration therapy.