BACKGROUND: The impact of undernutrition in dogs with protein-losing enteropathy (PLE) caused by inflammatory enteritis, intestinal lymphangiectasia, or both and which variables are most predictive of outcome are unknown. OBJECTIVES: Develop an undernutrition screening score (USS) for use at the time of diagnosis of PLE in dogs, which is predictive of outcome. ANIMALS: Fifty-seven dogs with PLE prospectively recruited from 3 referral hospitals in the United Kingdom. METHODS: An USS based on the presence and severity of 5 variables: appetite, weight loss, and body, muscle, and coat condition and scored out of 15, with higher scores reflecting worse undernutrition, was calculated at the time of diagnosis. Follow-up information was obtained for at least 6 months. RESULTS: Dogs that failed to achieve clinical remission within 6 months had higher USS at diagnosis compared with dogs that achieved remission (median, 7.5; range, 2-14 and median, 5; range, 0-14, respectively). The USS at diagnosis gave an area under the receiver operating characteristic curve (AUC) of 0.656 for predicting nonclinical remission within 6 months, whereas a score consisting of just epaxial muscle loss and coat condition resulted in a larger AUC of 0.728. CONCLUSIONS AND CLINICAL IMPORTANCE: Of the 5 variables assessed in the USS, a combination of epaxial muscle loss and coat condition was most predictive of not achieving clinical remission within 6 months in dogs with PLE. Additional studies will help determine the effect of changes in USS and the 5 associated variables after diagnosis on outcome variables in these dogs.