One of the most established areas in the field of healable polymeric materials is encapsulation-based healing agents. This chapter provides a comprehensive review of the range of chemical approaches to generating encapsulated healing agents; these systems are embedded into a host matrix, often in combination with catalysts or additional reagents. When the host matrix is subjected to damage, the embedded capsules are fractured, leading to release of the healing agents via capillary action; when in contact with the other reagents, this leads to polymerization in the damaged zones, thus regaining the physical integrity of the host matrix. This chapter describes the synthesis, characterization and applications of encapsulation-based healing agents.