In transthoracic and transesophageal echocardiography, a large multilobulated mass was present in the left atrium. An accidental pulmonary mass was also seen in a lung spiral CT scan. The cardiac mass was taken out, and a biopsy was obtained from the pulmonary mass. Adenocarcinoma was seen in histological assessment. Immunohistochemical staining was carried out to examine the expression of cytokeratin 7, cytokeratin 20, and caudal-related homeobox transcription factor 2 (CDX2) to determine the origin of the adenocarcinoma. In addition, the expression of these proteins was linked to the attributes of the patient and tumor. Post-surgery transesophageal echocardiography showed normal left ventricle and right ventricle function with no evidence of left atrium mass. Therefore, we suggest that asymptomatic cancer patients with a history of colorectal cancer and who have developed cardiac symptoms should be immediately examined for potential cardiac metastasis.