Objective Castleman disease, also known as giant lymph node hyperplasia, involves lesions in the lymph nodes usually located in the chest_ENREF_1, particularly in the mediastinum. Meanwhile, sinus bradycardia is a sinus rhythm slower than 60 beats per min, and it can occur in both healthy and sick individuals. However, the comorbidity of these two disorders has not been previously reported. In this paper, we report a case of a 46-year-old woman who presented with persistent sinus bradycardia and irondeficiency anemia. Diagnostic work-up revealed hepatosplenomegaly and a giant mass near the splenic hilum. The mass was removed surgically; after which, the patient’s bradycardia resolved immediately, while her anemia was corrected after subsequent chemotherapy. Pathological examination revealed lymph nodes with benign lesions, and the patient was diagnosed with hyaline-vascular variant of Castleman disease. This is the first documented case of sinus bradycardia associated with Castleman disease. In this paper, we describe the case characteristics, discuss the possible pathogenesis, and consider the appropriate treatment of symptomatic sinus bradycardia accompanying Castleman disease. Objective Castleman disease, also known as giant lymph node hyperplasia, involves lesions in the lymph nodes usually located in the chest_ENREF_1, particularly in the mediastinum. Meanwhile, sinus bradycardia is a sinus rhythm slower than 60 beats per min, and it can occur in both However, the comorbidity of these two disorders has not been previously reported. In this paper, we report a case of a 46-year-old woman who presented with persistent sinus bradycardia and irondeficiency anemia. Diagnostic work-up revealed hepatosplenomegaly and a giant mass near the splenic hilum. The mass was removed surgically; after which, the patient’s bradycardia resolved immediately, while her anemia was corrected after subsequent chemotherapy. Pathological examination revealed lymph nodes with benign lesions, and the patient was diagnosed with hyaline -vascular variant of Castleman disease. This is the first documented case of sinus bradycardia associated with Castleman di In this paper, we describe the case characteristics, discuss the possible pathogenesis, and consider the appropriate treatment of symptomatic sinus bradycardia accompanying Castleman disease.