Background <p>Melena is dark, tarry stools that typically indicate upper gastrointestinal bleeding. However, various dietary substances can alter stool color and potentially lead to diagnostic confusion. We present a rare case of stool discoloration caused by the ingestion of chocolate sandwich cookies.</p> Case presentation <p>A Black man in his 30s with a transverse colostomy presented with sudden-onset dark, tarry stool, raising concern for melena. Initial management included intravenous proton pump inhibitors and consideration of urgent endoscopy. However, the patient’s laboratory results and overall clinical presentation were inconsistent with upper gastrointestinal bleeding. Upon further questioning, he disclosed having recently consumed four packets of chocolate sandwich cookies. These cookies contain alkalized cocoa, which is rich in dark pigments that are poorly absorbed. We hypothesized that the stool was colored by the cookies and successfully reproduced the observed effect by having the patient eat the cookies a second time which led to another episode of dark black stool.</p> Conclusion <p>Awareness of dietary mimics of melena is crucial to avoid diagnostic errors and unnecessary interventions. This case highlights the importance of a thorough dietary history and the need for clinical caution before initiating treatment for presumed gastrointestinal bleeding in hemodynamically stable patients.</p>