Nutritional neuroscience is a newly developed multidisciplinary field of research exploring the intricate relationships between dietary intake, brain function, and mental health. The chapter below outlines how macronutrients (carbohydrates, proteins, and lipids) and micronutrients (vitamins, minerals, and antioxidants) regulate neurotransmission, neuroplasticity, and cognitive resilience. The gut-brain axis plays a critical role in the modulation of neuroinflammation and mood regulation, where diet affects the microbiota composition and, consequently, mental health outcomes. Dietary patterns such as the Mediterranean, Mediterranean–dietary approaches to stop hypertension intervention for neurodegenerative delay, and ketogenic diets have been linked with enhanced cognitive function and reduced risk of neurodegenerative disorder. In addition, the field of nutrigenomics recognizes the gene-derived foundation of food response in justification of personalized nutrition for mental well-being. The impact of processed food and excessive sugar intake on cognitive impairment, mood disorder, and neuroinflammation is also considered. New evidence sheds light on the therapeutic role of diet in prevention of neurological disorders and emphasizes the use of functional foods, fasting diets, and personalized supplementation. The chapter endeavors to bridge the knowledge gap between nutrition and mental health by encouraging precision-based dietary care to support brain health, emotional well-being, and neuroprotection.