Tranylcypromine is an effective antidepressant from the class of monoamine oxidase inhibitors and is structurally related to amphetamine. However, reports differ regarding the potential metabolism of tranyl cypromine to amphetamine and methamphetamine within the human body. We report a 25-year-old woman with severe depression who died due to a fatal tranylcypromine overdose in 2016. She had been prescribed tranylcypromine one day previously and had no history of previous suicide attempts or substance abuse. The body was transferred to a forensic medicine department in Tehran, Iran for the autopsy. A urine sample was positive for tranylcypromine, amphetamine and methamphetamine using gas chromatography/mass spectrometry after derivatisation with heptafluorobutyric acid. As amphetamines were present in the urine sample, it was assumed that the tranylcypromine had been converted to amphetamines metabolically. As such, it is possible that the legitimate use of certain prescription drugs may complicate the interpretation of test results for illegal drugs.