Patients presenting to the emergency department (ED) after medication overdose are often given activated charcoal initially for gastrointestinal decontamination. Complications of charcoal are rare, but do occur. The following case describes a patient with pre-existing undiagnosed diverticular disease who developed sigmoid perforation after a single dose of activated charcoal, given without cathartic for a drug overdose. A literature search revealed no other cases of bowel perforation associated with single-dose activated charcoal. This case report discusses adverse effects associated with activated charcoal and the role of cathartics in gastrointestinal decontamination.