A large amount of unstructured data is available in software artifacts, such as, documentation, developer discussions, source code, customer support requests, etc. This data contains important information that could be useful for developers in the context of several software engineering tasks. However, due to the large amount of unstructured data available today in software projects, the task of mining it can be challenging. The 5th Workshop on Mining Unstructured Data (MUD 2015) aims to stimulate discussion between researchers in the field about addressing the challenges posed by mining unstructured software data, to encourage cross-fertilization from different research domains, including NLP, IR, Machine Learning, etc. and to document and advance the state of the art of MUD. MUD 2015 is a full-day workshop and will include keynotes, tutorials, paper presentations, and more! The workshop will be held on September 28th, 2015. It is co-located with the 31st International Conference on Software Maintenance and Evolution (ICSME 2015) and will take place in Bremen, Germany.