The integration of pharmacogenomics in clinical practice offers enormous potential for transforming precision medicine by tailoring treatment to the specifics of individual genetic makeup. Data sharing and exchange of information for pharmacogenomics, however, faces some of the greatest challenges in terms of issues concerning privacy, data integrity, and governance. The proposed blockchain-based framework overcomes these challenges by assuring the secure, decentralized, and efficient sharing of pharmacogenomic data among healthcare providers, researchers, and patients. It uses symmetric encryption and homomorphic encryption to protect patient privacy, digital signatures, and smart contracts to manage patient consent as well as access control. The system deployed on the permissioned blockchain with the Practical Byzantine Fault Tolerance consensus protocol had very strong levels of security and reliability. Simulations showed that the framework preserves acceptable levels of transaction latency and throughput in a 10-node network, averaging 1.8 s latency and 275 transactions per second. Smart contracts also enable the efficient management of consent with minimal overhead. Overall, the proposed framework provides a strong solution for the secure sharing of pharmacogenomic data, thereby opening a pathway for the improvement in the adoption of precision medicine while keeping intact the nature and integrity of patient data.