Melatonin is widely recognized as a natural sleep aid, playing a crucial role in regulating circadian rhythms and promoting restful sleep. As a hormone naturally produced by the pineal gland in response to darkness, melatonin supplementation is commonly used to combat insomnia, jet lag, and other sleep disturbances. However, as its popularity has grown, so have concerns regarding its potential cognitive side effects. One of the most frequently reported issues is brain fog—a condition characterized by sluggish thinking, forgetfulness, and difficulty concentrating. This raises a critical question: can melatonin cause brain fog, and if so, what mechanisms underlie this effect? Understanding the relationship between melatonin and cognitive clarity requires an exploration of how melatonin interacts with neurotransmitters, sleep cycles, and brain function. While melatonin is essential for sleep regulation, its overuse or misuse may lead to unintended consequences, including grogginess and mental fatigue. This article delves into the science behind melatonin's effects on cognition, the potential causes of melatonin-induced brain fog, and strategies to mitigate its impact while maintaining optimal brain health.