Over the past two decades, the rapid development of cells encapsulated hydrogels and self-assembled hydrogels have been sources of attraction in several biomedical fields in order to control various aspects of human-related diseases and tissue regeneration and repair (surgery). Polymer hydrogels are composed of several natural, synthetic polymers, and cross-linkers in order to form tissue-like elasticity, nontoxicity, biodegradability, biocompatibility, and swelling ability, which enhance their applicability in advanced medicine and cell biological applications. This chapter covers several important natural and synthetic polymers widely used as hydrogels and self-assembled hydrogels for cell encapsulation. Cells encapsulated self-assembled hydrogels, their recent developments, and their significances in various medical applications are also discussed.