V Mkhitarian, D Pavlyuk and S Sidorov This volume contains the papers presented at CMDM 2020: The Fifth Workshop on Computer Modelling in Decision Making which was a big success by holding via online platform on November 26-27, 2020. The CMDM 2020 workshop brought together researchers, postgraduate students and academics interested in computer and mathematical modelling in decision making in different areas. The CMDM 2020 workshop’s main topics were computer and mathematical modeling for decision support in solving problems arising in industry, engineering, finance, insurance, as well as decision support methods and tools for data analysis, machine learning, forecasting, analytics, and their applications.The workshop was co-organized by Saratov State University (Saratov, Russia), the Central Bank of the Russian Federation and the Department of Statistics and Data Analysis of Higher School of Economics (Moscow, Russia). The CMDM 2020 workshop was held online due to the pandemic of COVID-19 and was co-located with the IX International Research and Practice Conference on Mathematical and Computer Modelling in Economics, Insurance and Risk Management, Saratov, Russia, November 25-28, 2020. The virtual format of the workshop was a first and novel attempt in this difficult year, but we are very satisfied that we have made it a success.Thirty two papers were submitted and twelve papers were accepted for presentation at the workshop after a careful peer reviewing process with discussions among reviewers and members of the program committee. All papers published in this volume of Journal of Physics: Conference Series have been peer reviewed through processes administered by the Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing. Each paper was reviewed by at least two reviewers or members of the program committee. We would like to thank all reviewers for their helpful efforts.The Editors, Vladimir Mkhitarian, Higher School of Economics, Moscow, Russia Dmitry Pavlyuk, Transport and Telecommunication Institute, Riga, Latvia Sergei Sidorov, Saratov State University, Saratov, Russia Program committee: Vladimir Mkhitarian, Higher School of Economics, Moscow, Russia – Co-chair Dmitry Pavlyuk, Transport and Telecommunication Institute, Riga, Latvia – Co-chair Sergei Sidorov, Saratov State University, Saratov, Russia – Co-chair Abraham Althonayan, Brunel University London, London, UK Vladimir Balash, Saratov State University, Saratov, Russia Tatiana Belkina, Russian Academy of Sciences, Moscow, Russia Sergei Dudov, Saratov State University, Saratov, Russia Boris Mirkin, Professor, Higher School of Economics, Moscow, Russia Yuri Blinkov, Saratov State University, Saratov, Russia