Good's syndrome is a rare, adult-onset immunodeficiency syndrome associated with thymomas. Here, we present a 71-year-old, previously healthy male with a history of opportunistic infections status postthymectomy, who presented with a septic knee complicated with bacteremia without any inciting factor. Therefore, a diagnosis of Good syndrome was made. While this is a rare disease, clinicians should have a high suspicion in patients with a history of thymoma. Early diagnosis and treatment can reduce opportunistic infections and improve morbidity and mortality.