Nostalgia, a complex emotion that arises from one's yearnful memories, involves multiple psychological processes. Cognitive neuroscience research has shed light on the neural mechanism of nostalgia as well as its adaptive functions. Nostalgia involves brain regions implicated in self-reflection, autobiographical memory, emotion regulation and reward processing. Also, nostalgia buffers various psychological and physical threats by modulating activities in brain regions implicated in emotion regulatory processing (i.e., both top-down emotion regulation and bottom-up sensory and attention processing) and reward processing. These findings deepen understanding of nostalgia and have implications for its application in clinical situations.