Myocarditis is a rare complication of therapy with mesalazine, a drug traditionally used in the treatment of inflammatory bowel disease. We report a case of a 32-year-old man with a recent diagnosis of ulcerative colitis, who presented to our hospital with chest pain and elevated troponin, 12 days following initiation of mesalazine. Diagnosis of myocarditis was confirmed with cardiac magnetic resonance imaging (CMR), which showed subepicardial gadolinium enhancement in the basal lateral/inferolateral segment of the heart. The patient's clinical condition improved upon stopping mesalazine and the follow-up CMR demonstrated resolution of the previous findings. Mesalazine can cause myocarditis early after initiation and clinicians should be aware of this rare yet serious cardiotoxic effect, as the discontinuation of the medication is the mainstay of treatment and leads to significant recovery.