Antimalarial agents are routinely used in the management of connective tissues diseases and various skin disorders. Ophthalmologic, neurological and digestive side effects of antimalarial agents are well known. However, cardiac toxicity is uncommon. We report a 49-year-old patient, treated with chloroquine for 21 years for a systemic lupus erythematosus and a discoid lupus, who presented a complete atrioventricular block that required implantation of a cardiac pacemaker in emergency. This patient did not have significant cardiovascular past medical history. Investigations excluded known causes of atrioventricular block and chloroquine toxicity was diagnosed. This case report illustrates the cardiotoxicity of synthetic antimalarial agents. A regular cardiovascular monitoring (especially with electrocardiogram) could be useful in patients receiving long-term treatment with antimalarial agents.