The hippocampus, a critical brain structure involved in memory, also plays a significant role in regulating anxiety-related behaviors. Recent advances in neuroimaging and animal models have provided insights into how dysregulation within hippocampal circuits can lead to heightened anxiety states. In this chapter, we summarize the complex anatomy of the hippocampus, highlighting its important subregions for anxiety-related behaviors, such as the dentate gyrus, CA1, and CA3, and their unique contributions to anxiety modulation. We explore the intricate neurotransmitter systems within the hippocampus, including glutamate, GABA, serotonin, and norepinephrine, elucidating their roles in neural circuitry and anxiety-related behavioral outcomes, and discuss the recent evidence on the hippocampal mechanisms of anxiety. The chapter also reviews key studies demonstrating the involvement of hippocampal neurogenesis and plasticity in anxiety, emphasizing the impact of environmental stressors and genetic predispositions. By synthesizing current research, we aim to provide a comprehensive understanding of how hippocampal dysfunction contributes to anxiety disorders and discuss potential therapeutic targets for ameliorating anxiety through modulation of hippocampal activity. In the last part of the chapter, information about Alzheimer’s disease and aging and changes in the hippocampus is given.