This book constitutes the refereed proceedings of the 5th International Symposium on NASA Formal Methods, NFM 2013, held in Moffett Field, CA, USA, in May 2013. The 28 revised regular papers presented together with 9 short papers talks were carefully reviewed and selected from 99 submissions. The topics are organized in topical sections on model checking; applications of formal methods; complex systems; static analysis; symbolic execution; requirements and specifications; probabilistic and statistical analysis; and theorem proving.