Infectious mononucleosis(IM) is a clinical syndrome characterized by fever, exudative tonsillitis, gerneralized lymphadenopathy(90% of cases), splenomegaly(50% of cases), and hepatomegaly(10% of cases). It is mainly caused by Epstein-Barr virus(EBV) and usually recovered completely in the majority of cases. The complications of IM are splenic rupture, pancreatitis, hematologic problems such as hemolytic anemia, aplastic anemia, and thrombocytopenia, neurologic problems such as meningitis, encephalitis, and Guillian-Barré syndrome, myocarditis, parotitis, orchitis, and interstitial pneumonitis, etc. Pulmonary involvement with EBV infection is rare condition reported frequency of 3% to 5%, in addition pleural effusion has been very rarely reported, especially in the pediatric population. We herein report a case of IM with pleural effusion in 3 years old boy with fever, cervical lymphnodes enlargement, and hepatosplenomegaly. And the pleural effusion is spontaneously resolved for a hospitalization period. A brief review of literature is included.