This volume constitutes the refereed proceedings of the 20th EuroSPI conference, held in Dundalk, Ireland, in June 2013. The 31 revised papers presented in this volume were carefully reviewed and selected. They are organized in topical sections on SPI Safety and Regulation Issues; SPI Lifecycle and Models; SPI Quality and Testing Issues; SPI Networks and Teams; SPI and Reference Models; SPI Implementation; Agile organisations and an agile management process group; Managing Diversity and Innovation; SPI and Measurement; Risk Management and Functional Safety Standards.