This book constitutes the refereed proceedings of the 5th International Workshop on Post-Quantum Cryptography, PQCrypto 2013, held in Limoges, France, in June 2013. The 17 revised full papers presented were carefully reviewed and selected from 24 submissions. The papers cover all technical aspects of cryptographic research related to the future world with large quantum computers such as code-based cryptography, lattice-based cryptography, multivariate cryptography, cryptanalysis or implementations.