FMCAD 2015 is the fifteenth in a series of conferences on the theory and applications of formal methods in hardware and system verification. FMCAD provides a leading forum to researchers in academia and industry for presenting and discussing groundbreaking methods, technologies, theoretical results, and tools for reasoning formally about computing systems. FMCAD covers formal aspects of computer-aided system design including verification, specification, synthesis, and testing. FMCAD was first held in 1996, and was a bi-annual conference until 2006, when the FMCAD and CHARME conferences merged into a single annual conference. Before merging, FMCAD was held in the United States on even years and its sister conference, CHARME, was held in Europe on odd years. Since 2006, the FMCAD conference has been held annually at various international venues.