Nanowhiskers of crystalline polysaccharides, including cellulose and chitin, have recently been attracting much attention, especially as rigid filler components of novel nanocomposite materials. Good dispersion of these nanowhiskers in aqueous suspensions, which are usually prepared by appropriate acid hydrolysis of native polysaccharide raw materials, has been examined based on two types of stabilization mechanisms, i.e., electrostatic and steric repulsions between nanowhiskers. In this review, recent results on electrostatic and steric stabilizations of nanowhiskers are introduced, together with brief and basic descriptions of nanowhiskers and these stabilization mechanisms. Some of the remarkable characteristics of nanowhiskers, such as viscosity behaviors, liquid-crystal formation, and nanocomposite formation, which are related to useful applications of these stable nanowhiskers, are also summarized.