OBJECTIVE To investigate whether lung ultrasonography (LUS) performed around the heart, where the lungs are in contact with the pericardium (ie, pericardial LUS), could be used for the diagnosis of cardiogenic pulmonary edema (CPE) in dogs with degenerative mitral valve disease (DMVD). ANIMALS 15 control dogs with healthy hearts and 26 dogs with DMVD. PROCEDURES In a prospective multicenter study design, dogs with DMVD were assigned to 2 groups: those with CPE (n = 11) and those without CPE (15). Thoracic radiography, echocardiography, and pericardial LUS were performed for all dogs. For pericardial LUS, the left ventricular short-axis view was obtained with a sector probe (dog positioned in right parasternal recumbency) and the number of B lines was recorded. Accuracy of pericardial LUS for the diagnosis of CPE was calculated, with thoracic radiography used as the reference standard. RESULTS On thoracic radiography, all dogs with CPE had a diffuse distribution of interstitial to alveolar pulmonary infiltrates. On pericardial LUS, most control dogs (14/15) and dogs with DMVD but no CPE (13/15) had ≤ 2 B lines, whereas all dogs with DMVD and CPE had ≥ 3 B lines. The presence of ≥ 4 B lines had high sensitivity (91%; 95% confidence interval, 62% to 98%) and excellent specificity (100%; 95% confidence interval, 89% to 100%) for the diagnosis of CPE, and the area under the receiver operating characteristic curve was 0.99. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that identification of ≥ 4 B lines extending from the epicardium of the left ventricle into the lung field on pericardial LUS may be useful in the diagnosis of CPE in dogs with DMVD. Additional research is needed to determine whether pericardial LUS allows differentiation between CPE and pneumonia.