A persistent 3,4-Methylenedioxymethamphetamine (MDMA) exposure may disrupt the human body serotonergic system which subsequently leads to physical and psychiatric chaos. Serotonin, a well-known monoamine neurotransmitter which is the main target of MDMA can be found in cerebrospinal (CSF) fluid. Its variation reflects the severity of neuronal damage caused by MDMA exposure. Hence, this article aimed to review the potential of serotonin as biomarker for neuronal damage posed by MDMA. Articles from main databases including PubMed, Scopus and Web of Science were analysed and its information about serotonin variation in cerebrospinal fluid in response to MDMA exposure were extracted. MDMA is affine to serotonergic system, and can represents as a change in the level of serotonin in the CSF. It provides critical information about underlying mechanisms of neuronal damage from neurotoxicity, neurodegenerative process, excitotoxicity and hallucination due to MDMA exposure. Since serotonin variation in the CSF reflects the severity of neuronal damages, serotonin is potentially be used as an early indicator to assess neural injury caused by MDMA that plays an important role in intervention purpose. Serotonin variation in the CSF reflects the severity of neuronal damages. Its variation in CSF can be used as a biomarker for assessing neuronal damage following MDMA exposure.