Key Clinical MessageSystemic lupus erythematosus (SLE) can have various manifestations. Although cardiac involvement is very common in SLE patients, a severe acute pericarditis as the first manifestation of SLE in a male patient is relatively rare. A 36‐year‐old male was admitted to our hospital with acute pericarditis, large circumferential fibrinous pericarditis, and major criteria of a high‐risk case of acute pericarditis. After a complete investigation, the underlying disease was revealed to be SLE. All of his symptoms were completely resolved after 6 weeks of treatment with non‐steroidal anti‐inflammatory drugs and corticosteroids with no need for a pericardiocentesis. Patients with acute fibrinous pericarditis should be considered and precisely investigated for multiorgan autoimmune process such as SLE, to avoid unnecessary intervention, and minimize the risk of recurrence and chronicity of the condition.