Jai Pal Mittal was born on 21 September 1940 in Meerut in the Indian state of Uttar Pradesh. He completed his graduate (BSc) and master's studies (MSc) in chemistry from the Agra University and migrated to Mumbai in 1959, looking for career opportunities. He joined the Training School of Atomic Energy Establishment, erstwhile Bhabha Atomic Research Centre and did a one-year course after which he moved to USA to join the Department of Radiation Chemistry of the University of Notre Dame, Indiana. He completed his doctoral studies (PhD) in 1967, under the guidance of A. A. Lamola and W. H. Hamill. Receiving an invitation from Willard Libby, the 1960 Nobel laureate in Chemistry, to assist him, Mittal did his post doctoral research, for over a year, at the Radiation and Nuclear Chemistry laboratory of the University of California.
In 1969, Mittal returned to India to start his career as a Pool Officer at the Bhabha Atomic Research Centre (BARC) and started working in the field of photochemistry. Two years later, in 1971, he got an opportunity to work with Professor E. Hayon at the United States Army Natick Soldier Research, Development and Engineering Center and worked there for one year. On his return to India in 1972, he formed a research group at BARC for research in photochemistry and radiation chemistry. During this period, he organized the first national symposium in Thiruvananthapuram, National Symposium on Fast Reaction Chemistry and Techniques.
Mittal continued at BARC to become the Director of Chemistry and Isotope Group and the DAE Raja Ramanna Fellow of the institution. He also holds the position of M. N. Saha Distinguished Professor of the National Academy of Sciences, India and the post of a Distinguished Professor at the University of Pune and the Indian Institute of Technology, Mumbai. During his tenure at BARC, he is known to have contributed for the establishment of a nanosecond LINAC based pulse radiolysis system at BARC and promoted the nano, pico and femtosecond pump and probe techniques to study the chemical dynamics. He is reported to have initiated a new school of research in Radiation Chemistry and Photochemistry in India and his group was successful in isotopic enrichment of hydrogen, carbon and uranium isotopes. His research findings have been recorded by way of over 300 scientific papers, published in peer reviewed journals and ResearchGate, an online scientific data repository, have listed 250 of them. He has also mentored many students in their doctoral studies.
Mittal has been associated with the Board of Research in Nuclear Sciences as a chairman of many of its basic sciences committees. He is a former president of the Indian Society of Radiation and Photochem Sciences (1997-2001), the National Academy of Sciences, India (2003–04) and the Asian Photochemistry Association (2003- 2008). He has also served the Indian National Science Academy as a council member (1998-2000) and as an additional member (2005–06). He serves as the president of the Asian and Oceanian Photochemistry Association and is a member of the education council of the University of Allahabad. He is a life member of the Indian Chemical Society where has also been a past president.
Mittal lives in Navi Mumbai in Maharashtra and continues attending seminars and conferences to deliver keynote addresses.