Yellow nail syndrome (YNS) is an uncommon condition characterized by nail changes, lymphedema, in addition to pulmonary disorders and pleural effusion. Pericarditis and non-cardiac disorders can evolve with pericardial effusions including autoimmune conditions, hypothyroidism, malignancies, tuberculosis, and uremia. A 72-year-old Brazilian woman under treatment for arterial hypertension and hypothyroidism was admitted with pericarditis and pericardial effusion concomitant with yellow nail syndrome. She denied tobacco smoking, alcohol abuse, and similar disorders in her family. Clinical and complementary evaluation ruled out infectious diseases, malignancies, and autoimmune disorders as etiologic factors in this case. Hypothyroidism is a well-known cause of pericardial effusion, the vast majority in the absence of pericarditis, and has been described as an associated condition in some individuals with YNS. Case studies might contribute to better understanding of these causal or casual relationships.