During the past decade, much work has been devoted to the preparation of nanomaterials by blending starch nanocrystals from different sources with various polymer matrices. The following paper summarizes the most up-to-date information available relating to starch nanocrystals and their contribution to research, application, and advancement of diversified nanomaterials. This paper provides an overview of aspects related to starch nanocrystals, including methods for extraction and preparation, chemical modification (with particular emphasis on the modification methods and strategies), reinforcing effects and mechanisms, and applications and prospects.