The rapid rise of mobile financial apps has completely changed the landscape of financial services, opening up amazing opportunities, but also bringing along some serious security challenges. This paper dives into the essential security frameworks that are crucial for Fintech mobile applications, honing in on three main areas: advanced fraud detection methods, secure payment processing protocols, and the requirements for regulatory compliance. By thoroughly analyzing current security technologies and regulatory frameworks, this study assesses how effective machine learning-based fraud detection systems, blockchain-enabled payment security, and multi-layered authentication protocols really are. The research employs a mixed-methods approach, blending a systematic literature review with case studies of top Fintech platforms. The results show that AI-driven fraud detection systems achieve an impressive 94% accuracy in spotting fraudulent transactions, while multifactor authentication cuts down unauthorized access by 87%. However, the landscape of regulatory compliance is still quite fragmented across different jurisdictions, which poses implementation challenges. The findings suggest that integrated security architectures that combine behavioral analytics, biometric authentication, and real-time monitoring offer the strongest protection for mobile financial applications. This research adds to our understanding of the comprehensive security frameworks needed for sustainable growth in Fintech, all while keeping user trust and regulatory compliance in check.