The two-volume set LNCS 15751 + 15752 constitutes revised selected papers from the 29th International Conference on Financial Cryptography and Data Security, FC 2025, which took place in Miyakojima, Japan, during April 14–18, 2025.The 42 full papers, 3 short papers and 1 Systematization of Knowledge paper included in the proceedings were carefully reviewed and selected from 300 submissions. They were organized in topical sections as follows:Part I; Layer 2; DeFi; zero-knowledge and its applications; modeling Bitcoin and incentives; efficient blockchains; broadcast; encryption and its applications; Part II: MEV; consensus; proof-of-X and rewards; signatures and threshold cryptography; machine learning.