The advent of quantum computing technology has posed a new threat to traditional cryptographic algorithms applied in blockchain protocols. This paper presents a new post-quantum consensus protocol that will aid blockchains to achieve security in the age of quantum computing. We propose, in this paper, the provision of quantum-resistant cryptographic algorithms, such as lattice-based and code-based cryptography, for application with existing blockchain consensus mechanisms. Our methodology is a design of post-quantum blockchain, an implementation in the simulated environment, and performance evaluation based on metrics such as block validation time, transaction throughput, and security against quantum computing threats. The results indicate that although there is a minor performance overhead of roughly 12% increase in block validation time, the proposed protocol achieves high security with 100% resistance to quantum-based attacks such as Shor’s algorithm and Grover’s algorithm. In terms of scalability, post-quantum blockchain maintains reasonable performance across different network sizes with a maximum 10% decrease in transaction throughput. This therefore goes on to demonstrate that the concept of post-quantum security within blockchain systems can indeed be very possible while keeping an effective balance between scalability and security with quantum computing.