Prasad Modak holds B Tech (Civil Engg), M Tech (Environmental Science and Engg) from Indian Institute of Technology (IIT) Bombay and Doctor of Engg (Environmental Engg) from Asian Institute of Technology, Bangkok. He was a Professor at Centre for Environmental Science & Engineering at IIT Bombay (1984-1994) and later as Professor (Adjunct) at the Center for Technology Alternatives in Rural Areas (CTARA) (2009-2017). He is currently the Managing Director of Environmental Management Centre Pvt Ltd. and Director of Ekonnect Knowledge Foundation. He is also Professor in Practice at Grantham Research Institute at London School of Economics, London, UK He has worked with almost all key UN, multi-lateral and bi-lateral developmental institutions in the world. These include the World Bank, IFC, Asian Development Bank (ADB), Asian Infrastructure Investment Bank (AIIB), European Investment Bank (EIB), UNEP, UNIDO, UNITAR, UNDP, UNOPS, DFID, BII etc and intergovernmental organizations such as the Asian Productivity Organization, Tokyo. Apart from Government of India and various State Governments, Dr Modak's advice is sought by Governments of Bangladesh, Egypt, Indonesia, Mauritius, Thailand and Vietnam. He has published several journal articles, chapters and books on environmental management.

His book on EIA for Developing Countries was published by UN University (1999) and later reprinted by Oxford University Press (2005). His book "Environmental Management Towards Sustainability" was published in December 2017 with CRC Press of Taylor and Francis Group. His book on Practicing Circular Economy for the CRC Press was released in June 2021.