Nanogels are hydrogels with nanometer-scale three-dimensional networks of physically or chemically cross-linked chains. Nanogels have attracted much interest in recent years for various biomedical applications such as drug delivery systems and bioimaging owing to their specific properties of size tunability and intrinsic hydrophilic surfaces. Nanogels are generally classified either as natural polymer-based or synthetic polymer-based nanogels. Natural polymer-based nanogels are considered better candidates for drug delivery than synthetic polymer-based nanogels. This review summarizes the role of natural polymer-based nanogels, especially carbohydrate-based nanogels as drug and gene delivery systems.