<p>Cell encapsulation technology is a cornerstone of cell-based therapies, offering immunoprotection and controlled microenvironments for transplanted cells. However, its clinical translation remains hindered by immune rejection, foreign body response (FBR), and hypoxia. Inspired by nature, functional polymer-based biomimetic strategies have emerged to overcome these barriers. This review highlights three major directions: (i) extracellular matrix (ECM)-mimetic hydrogels that reproduce structural and biochemical cues to support cellular viability and function; (ii) immune-modulatory and antifouling interfaces inspired by cell membranes, zwitterions, and tissue adhesives to alleviate FBR and prolong graft survival; and (iii) oxygenation strategies incorporating microchannel networks and artificial oxygen carriers to sustain metabolic activity. Beyond these, we also discuss multifunctional integration and fabrication technologies that enable scalable and intelligent encapsulation systems. Finally, we provide perspectives on translational challenges, emphasizing the role of functional polymers in advancing biomimetic encapsulation toward clinically viable cell-based therapies.</p>