Abstract: Depression is a severe emotional disorder characterized by persistent and prominent clinical symptoms, such as sadness and a loss of interest or pleasure. The pathogenesis of depression is intricate, and in recent years, investigations into the gut-brain axis theory have offered viable endogenous mechanisms for further exploration of depression. This theory is supported by evidence of disrupted gut microbiota, elevated inflammation markers, and deviant neurotransmitter levels in individuals with depression. Plant polysaccharides exhibit various biological activities and have been shown to modulate different metabolic pathways within the gut microbiota, thus impacting depression through the gut-brain axis. Nevertheless, a comprehensive summary of their mechanisms of action is currently lacking. Therefore, this study explores the potential antidepressant effects of plant polysaccharides by examining their regulation of short-chain fatty acids, lipopolysaccharides, and tryptophan metabolism within the gut microbiota and the gut-brain axis. Through a comprehensive analysis of recent literature, this article reviews the intricate relationships between various plant polysaccharides and their mechanisms in alleviating depression. It provides a theoretical basis for understanding how plant polysaccharides act as antidepressants and for developing resources for antidepressant polysaccharides.