Myopericarditis is an infrequent complication of acute diarrheal illness due to Campylobacter jejuni, and it has been mainly reported in developed nations. The first case detected in Chile--an upper-middle income country--that is coincidental with the increasing importance of acute gastroenteritis associated to this pathogen, is described. Recognition of this agent in stools requires special laboratory techniques not widely available, and it was suspected when a young patient presented with acute diarrhea, fever, and chest pain combined with electrocardiogram (EKG) abnormalities and elevated myocardial enzymes. C. jejuni myopericarditis can easily be suspected but its detection requires dedicated laboratory techniques.