This book chapter explores the crystallization behavior of nanoclay-containing polymer nanocomposites, a topic of growing importance in materials science and polymer chemistry. These nanocomposites have unique properties such as enhanced mechanical strength, improved thermal stability, and barrier properties arising from nanoclay inclusion. The chapter discusses the nucleation effect of nanoclay, its role in promoting crystalline regions, and its impact on crystalline morphology. It also examines the kinetics of crystallization, thermal properties, barrier properties, rheological properties, and surface modification techniques. The chapter provides valuable insights for researchers, engineers, and materials scientists seeking to understand and tailor these materials for various applications.