This is a retrospective study over a 5-year period from January 1, 2013 to December 31, 2018. The diagnosis of cardiothyreosis was retained before clinical signs of hyperthyroidism confirmed to biology by an elevation of T4 and a collapse of ultrasensitive TSH associated with at least one of the following heart failure: insufficiency heart disease, coronary heart failure, rhythm disorder. Sociodemographic, anthropometric, clinical and paraclinical data were analyzed from medical records. Follow-up was evaluated over a period of 6 months to one year after being put on synthetic antithyroids. Results: Of 72 patients seen with hyperthyroidism conditions during the period, we identified 10 cases of cardiothyresis at the departments of Endocrinology and Cardiology of the CNHU/HKM Teaching hospital of Cotonou, Benin. The frequency of cardiothyreosis among hyperthyroidsis was 13.88%. The mean-age for our patients was 50.9 years with bounds from 29 to 79 years. The predominance was female, 8 women for 2 men. A clinical background of high blood pressure is founded in 6/10 patients; 4/10 had a history of hyperthyroidism. All patients had heart failure associated with complete arrhythmia by atrial fibrillation in 6 patients. The multi-modular goiter was found in 5/10 of the patients, the vascular goiter 5/10. Synthetic antithyroids, hygienic-dietary measures and a specific treatment for heart failure were used. The average length of hospital's stay was 7 days. Immediate development is satisfactory with euthyroidism in all patients and improved functional signs. Conclusion: Cardiothyreosis is infrequent in Cotonou. This is a serious complication of hyperthyroidism, which is expensive to manage. Hence the need for early diagnosis and effective treatment of hyperthyroidism.