Dietary therapy plays an important role in the management of canine idiopathic diarrhoea (ID). The objective of this study was to determine if a unique dietary formulation (Food A) containing antioxidants, n-3 fatty acids, resistant banana starch, and stable glutamine source is effective for management of canine ID. Eighteen dogs with chronic diarrhea for which an extensive diagnostic investigation could not identify a cause, were randomly allocated to treatment with wet followed by dry formulations of Food A or an alternative food marketed for gastrointestinal distress (Food B). Each food was fed for 3 weeks in a double-blinded, crossover fashion. Owners recorded faecal grade (1=liquid, 5=firm), vomiting, and appetite daily. A questionnaire and re-examination were completed at the end of each food trial. Seventy-six and 71% of dogs fed wet and dry formulations of Food A had > 1 faecal grade improvement within 7 days of dietary intervention. Owner satisfaction was 78-86%, with 56-77% reporting improved quality of life for Food A. The frequency of grade 4-5 faeces was higher for wet (A: 56.2%, B: 61.4%) and dry foods (A: 78.2%, B: 82.9%) compared to baseline (41.3-46.6%). Mean ± SE faecal grades were significantly higher for dry foods (A: 4.1±0.3, B: 4.3±0.3) but were not different for wet foods (A: 3.6±0.2, B: 3.6±0.2), compared to baseline (wet: 3.3±0.2, dry: 3.2±0.3). These results indicate that Food A is effective in improving faecal consistency, owner satisfaction, and perception of quality of life for most dogs with chronic ID.