Mobile payment systems have become a cornerstone of modern digital commerce, processing over $1.2 trillion in transactions globally by 2023. However, the centralized nature of these systems presents critical vulnerabilities to fraud, data breaches, and system failures. This paper proposes a novel blockchain-based architecture that addresses these challenges through three key innovations: (1) a decentralized consensus mechanism optimized for mobile transactions, (2) a real-time synchronization protocol that maintains data consistency between mobile devices and the blockchain network, and (3) an adaptive scaling framework that dynamically adjusts to transaction volume. Experimental results from stress testing with 2,000 concurrent users demonstrate that our system achieves 99.7% uptime, reduces transaction fraud by 94% compared to traditional systems, and maintains sub-second latency (average 0.7s) even under peak loads. Performance analysis shows 30% lower CPU utilization and 25% better memory management compared to leading mobile payment applications, while maintaining robust security standards. These findings demonstrate that our blockchain-based approach not only enhances security and reliability but also achieves the scalability and efficiency required for widespread adoption in modern digital payment ecosystems. The proposed architecture provides a foundation for future research in secure, scalable mobile payment systems.