Spleen gathers numerous functions and plays a critical role in immunity against encapsulated bacteria. Anatomical injuries or physiological spleen dysfunctions can lead to complete (asplenism) or partial (hyposplenism) functional deficits and expose the patient to the risk of fulminant sepsis, as well as to thromboembolic complications. The purpose of this article is to provide the primary care physician with the tools needed to identify functional disorders of the spleen and to prevent their complications. The latest recommendations for antibiotic prophylaxis and immunization are also addressed.