Hydatid cyst inside the cardiac chambers, especially the right ventricle, is a rare manifestation of the Echinococcus granulosus infection. We present a rare case of a mobile hydatid cyst on the chordae tendineae of the right ventricular papillary muscle. An 11-year-old male patient presented with multiple cysts in the body (numerous ones in the lung and liver) who had undergone left lung lobectomy due to a hydatid cyst prone to rupture. In the subsequent echocardiography, a fully mobile cyst measuring 2×1.5 cm was noticed in the right ventricle. Although the child had no cardiac presentation, due to the risk posed by its location and the high probability of sudden death or embolism, he underwent a successful cardiac and pulmonary bypass operation, and the cyst was completely excised. It was located on the chordae tendineae of the papillary muscle. In agricultural and rural countries and regions, cardiac hydatid cysts should be considered at any age. Due to the high risk of complications and mortality in cardiac hydatid cysts, regardless of the symptoms, inpatients with a positive history, cardiac examination with echocardiography must be included in diagnostic protocols. These cysts should be surgically removed as soon as possible on diagnosis, regardless of the symptoms.