Introduction:Cardiac cysts in hydatid cysts, a parasitic disease, are extremely rare, and left-atrial hydatid cysts are even more unusual. Therefore, the authors report herein a rare case of a hydatid cyst in the left atrium. According to them, this is the third documented case of left-atrial hydatid cysts. Presentation of Case:A 25-year-old male presented at the outpatient clinic with atypical chest pain, hacking cough, dyspnoea, nausea, and vomiting for 2 months. Echocardiography showed a left-atrial unilocular, well-delineated mass. The authors also found multiple liver cysts and spleen cysts. Discussion:The widespread distribution of the disease in our regions, the dog contact story of the patient, and the appearance on echocardiograms were strong reasons to diagnose a hydatid cyst in the left atrium, which may cause many symptoms (bundle branch conduction, arrhythmias, myocardial infarction) or unexpected death. Conclusions:The authors aimed to report this case due to the disease's high probability of death, even asymptomatic patients with cardiac hydatid disease should all be referred for early surgery.