We had experienced a case of pericarditis associated with Mycoplasma and Salmonella co-infection. This 5-year old boy presented with high fever and generalized tonic-clonic seizure. The diagnosis was based on the markedly increased serial titer of Widal test and cold agglutinin with Mycoplasma indirect hemmagglution test during hospitalization. The electrocardiogram revealed P-R interval prolongation and an echocardiogram revealed moderate pericardial effusion. The patient treated with ceftriaxone and erythromycin for 2 weeks, and responded to the treatment well. We report this case with brief review of the related literatures.