OBJECTIVE To compare signalment, clinical signs, diet, echocardiographic findings, and outcome for pit bull–type breeds diagnosed between 2015 and 2022 with dilated cardiomyopathy (DCM) or with DCM diagnosed by a cardiologist but that did not meet all study echocardiographic criteria (DCM-C). ANIMALS 91 dogs with DCM and 11 dogs with DCM-C. PROCEDURES Data were collected on clinical findings, echocardiographic measurements, and diet at the time of diagnosis (for 76/91 dogs); echocardiographic changes; and survival. RESULTS For dogs with diet information available for time of diagnosis, 64/76 (84%) dogs were eating nontraditional commercial diets, while 12/76 (16%) were eating traditional commercial diets. There were few differences between diet groups at baseline, with congestive heart failure and arrhythmias common in both groups. Thirty-four dogs with known baseline diet and diet change status had follow-up echocardiograms between 60 and 1,076 days later (traditional diet, n = 7; nontraditional diet that changed diets, 27; and nontraditional diet group without diet change, 0). Dogs in the nontraditional diet group that changed diets had a significantly greater decrease in normalized left ventricular diameter (diastolic, P = .02; systolic, P = .048) and the left atrium-to-aorta ratio (P = .002) and a significantly greater increase in fractional shortening (P = .02) compared to dogs eating traditional diets. Dogs eating nontraditional diets with diet change (n = 45; P < .001) and dogs eating traditional diets (12; P < .001) had a significantly longer survival time compared to dogs eating nontraditional diets without diet change (4). Dogs with DCM-C also had significant echocardiographic improvements after diet change. CLINICAL RELEVANCE Congestive heart failure and arrhythmias were common in pit bull–type breeds with DCM. Those eating nontraditional diets that changed diets had significant improvements in echocardiographic measurements after diet change.