Congenital secundum atrial septal defect (ASD) and membranous ventricular septal defect (VSD) were diagnosed in a 1-day-old Holstein-Friesian calf necropsied in the Department of Pathology of Mehmet Akif Ersoy University. The secundum atrial septal defect was 32.9 x 23.1 mm in width and was elliptical. The membranous ventricular septal defect was 25.3 x 18.5 mm in width and was round to oval in shape. Both atrial and ventricular septal defects were stained with hematoxylin-eosin and Van Gieson's stain. Histopathological examination showed that the defects mainly consisted of numerous muscle cells and, in some areas, dense fibrous connective tissue.