This book constitutes the thoroughly refereed post-proceedings of the 5th International Conference on Software Language Engineering, SLE 2012, held in Dresden, Germany, in September 2012. The 17 papers presented together with 2 tool demonstration papers were carefully reviewed and selected from 62 submissions. SLE's foremost mission is to encourage and organize communication between communities that have traditionally looked at software languages from different, more specialized, and yet complementary perspectives. SLE emphasizes the fundamental notion of languages as opposed to any realization in specific technical spaces.