Accumulating evidence indicates that diet and nutrition are important modifiable risk factors for the prevention and treatment of mental health disorders. However, the neural mechanisms underlying nutrition's effects on mental health remain to be well established. The interdisciplinary field of nutritional cognitive neuroscience integrates methods across the nutritional, cognitive, and brain sciences to understand nutrition's impact on brain health across the lifespan, with recent applications to the study of mood and anxiety-related disorders. In this focused review, we begin by investigating the neural mechanisms underlying mood and anxiety-related disorders, surveying evidence of alterations within specific structural and functional networks. We then review emerging evidence to suggest that the structure and function of these networks are influenced by specific nutrients that may confer beneficial effects, including B-vitamins, omega-3 polyunsaturated fatty acids, polyphenols, and carotenoids. In this effort, we highlight plausible biological pathways through which diet may influence mood and anxiety-related disorders. We conclude by presenting directions for future research, emphasizing the need for dietary interventions that incorporate contemporary methods from cognitive neuroscience and nutritional epidemiology to promote brain health and reduce the risk of mental illness.