Median sternotomy surgery stands as one of the prevailing strategies in cardiac surgery. In this study, the cutting‐edge bone adhesive is designed, inspired by the impressive adhesive properties found in mussels and sandcastle worms. We have created an osteogenic nanocomposite coacervate adhesive by integrating a cellulose‐polyphosphodopamide interpenetrating network, quaternized chitosan, and zinc, gallium‐doped hydroxyapatite nanoparticles. This adhesive is characterized by robust catechol–metal coordination which effectively adheres to both hard and soft tissues with a maximum adhesive strength of 900 ±38 kPa on the sheep sternum bone, surpassing that of commercial bone adhesives. The release of zinc and gallium cations from nanocomposite adhesives and quaternized chitosan matrix imparts remarkable antibacterial properties and promotes rapid blood coagulation, in vitro and ex vivo. It is also proved that this nanocomposite adhesive exhibits significant in vitro bioactivity, stable degradability, biocompatibility, and osteogenic ability. Furthermore, the capacity of nanocomposite coacervate to adhere to bone tissue and support osteogenesis contributes to the successful healing of a sternum bone defect in a rabbit model in vivo. In summary, these nanocomposite coacervate adhesives with promising characteristics are expected to provide solutions to clinical issues faced during median sternotomy surgery.This article is protected by copyright. All rights reserved