The clinical need for bone grafts that conform to irregular defects like alveolar clefts is rapidly increasing. We developed a moldable bone-regenerating putty (HAp-E-COD₂E) by combining hydroxyapatite (HAp) with a polyelectrolyte coacervate system, COD₂E, composed of dopamine-functionalized fucoidan and poly-L-lysine. Catechol groups enabled strong metal–coordination bonding with hydroxyapatite (HAp), enhancing formability and structural integrity. COD₂E also functioned as a delivery platform for bone-regenerating exosomes (E-COD₂E), preserving their membrane integrity and enabling sustained release. This improved cellular uptake and reduced the need for repeated administration, addressing key limitations of conventional exosome therapies. By integrating controlled release, material adaptability, and osteoconductive coating, this coacervate-based system offers a promising strategy for effective bone tissue regeneration.