This book constitutes the refereed proceedings of the 9th International Conference on Cryptology and Information Security in Latin America, LATINCRYPT 2025, held in Medellín, Colombia, in October 2025.The 17 full papers included in this book were carefully reviewed and selected from 41 submissions.They were focused on the following topical sections: Position Paper; Zero-Knowledge Proofs and Distributed Computation; Quantum and Post-Quantum Cryptography; Symmetric-Key Cryptography and Attacks; Machine Learning and Cryptanalysis; and Implementation and Efficiency.