A nine-year-old female McDowell's carpet python (Morelia spilota mcdowelli) presented with an eight-month history of anorexia. A rostral subcutaneous abscess was diagnosed by cytology and surgical excision was elected. During ultrasound-guided cardiocentesis for pre-anaesthetic blood work, severe right atrial dilation and hypokinesis, thickened and irregular atrio-ventricular valves, ventricular myocardial hyperechoic foci and subjective ventricular hypokinesis were observed. Spontaneous echo contrast (SEC) was observed inside the right atrial cavity. Echocardiographic lesions were consistent with restrictive cardiomyopathy previously described in a case report involving the same subspecies, with additional concurrent thrombus formation. SEC has not been previously described in reptiles, and the presence of simultaneous SEC and restrictive cardiomyopathy suggests that it might be predictive of thrombus formation, as is the case in mammals. Following surgical excision of the rostral abscess, anorexia resolved, suggesting asymptomatic cardiopathy despite severe cardiac lesions. Further studies are needed to confirm the prevalence of cardiac diseases in reptiles and whether severe cardiac disease can be asymptomatic in captive snakes. Routine echocardiography in asymptomatic snakes with non-specific signs is encouraged.