A systematic description of the history, clinical and radiographic signs, and clinical sequelae in 13 dogs and four cats with congenital peritoneopericardial diaphragmatic hernia (CPDH) seen over ten years is presented. The predominant signs were gastrointestinal and respiratory. The animals were 8 weeks to 10 years old. Eight of the 13 dogs were male; the four cats were female. Weimaraners were 30.8 percent of the affected dogs, but only 1.1 percent of the hospital population during the ten years reviewed. There were concurrent umbilical hernias in four dogs, congenital heart disease in two dogs, and sternal deformities in six dogs and one cat. Twelge of the 13 dogs and two of the four cats had survey radiographs. Superimposed diaphragmatic and caudal heart borders were seen in nine of the 12 dogs and both cats. Abnormal soft‐tissue gas or double soft‐tissue densities in the pericardial sac were seen in 11 of the 12 dogs and the two cats. Upper gastrointestinal studies, pneumoperitoneography, thoracic tomography, and right ventricular angiography were special studies used to evaluate CPDH. Surgical correction was successful in nine of 11 dogs; signs remained in two dogs. The longest postoperative survival was 6.5 years. A 14‐week‐old English Setter without surgical correction of its CPDH or pulmonic stenosis was free of clinical signs of either disease for 2.5 years. Twenty‐five reports of CPDH from 1960 to 1979 are reviewed.