ABSTRACT: BACKGROUND:Acute diarrhea is a common clinical presentation of dogs. The effect of specific anti-diarrheal probiotic pastes (ADPPs) in the management of acute, uncomplicated diarrhea in dogs is unknown. HYPOTHESIS:Administration of an ADPP containing Enterococcus faecium 4b1707 will improve the clinical outcome of acute, uncomplicated diarrhea in dogs compared to placebo. ANIMALS:One hundred forty-eight client-owned dogs with acute diarrhea as the main clinical sign. METHODS:Double-blinded, placebo-controlled, randomized, blocked, multicenter clinical field study conducted at 14 primary care veterinary practices in the United Kingdom and Ireland. RESULTS:The ADPP was associated with better clinical outcome compared to placebo in dogs with acute, uncomplicated diarrhea. Dogs in the ADPP group had a significantly shorter duration of diarrhea (ADPP: median, 32 hours; 95% confidence interval [CI], 2-118; n = 51; Placebo: median, 47 hours; 95% CI, 4-167; n = 58; P = .008) and the rate of resolution of diarrhea was 1.60 times faster in the ADPP group than in the Placebo group (ratio, 1.60; 95% CI, 1.08-2.44; P = .02). Fewer dogs required additional medical intervention (AMI) for non-improvement or worsening in the ADPP group compared to the Placebo group (3.5% of dogs and 14.8% of dogs, respectively), with a relative risk of 0.88 (P = .04; AMI, ADPP, 3.5%, 2/57 dogs; Placebo, 14.8%, 9/61 dogs; relative risk, 0.88; 95% CI, 0.77-0.99). CONCLUSION AND CLINICAL IMPORTANCE:The ADPP may accelerate resolution of acute diarrhea in dogs and decrease the requirement for AMI.