With the aging of society and changes in lifestyle, the incidence of neurological diseases (NDs) has been increasing year by year, bringing a heavy burden to patients and society. Although the efficacy of chemical drugs in the treatment of NDs is remarkable, there are problems such as high side effects and high costs. Therefore, finding mild and efficient drugs for NDs treatment has become an urgent clinical need. Natural source polysaccharides (NSPs) are macromolecules with unique bioactivity and low toxicity characteristics, which have great potential to become novel therapeutic agents for NDs. In the present study, the pharmacological activities and potential molecular mechanisms of NSPs to alleviate NDs are systematically reviewed from the perspectives of inflammation, oxidative stress, apoptosis, neuronal cell autophagy, neurotoxicity, and sedation-hypnosis. In addition, the limitations of the existing studies were analyzed and discussed, and the future research direction was suggested. This study may provide scientific basis for the research and development of therapeutic agents for NDs based on NSPs.