Pathria obtained his BSc Honours and MSc Honours degrees from
Panjab University,
Hoshiarpur in July 1953 and July 1954, respectively, and soon thereafter, at the invitation of Professor F.C. Auluck, joined the graduate school of Physics at the
University of Delhi for his doctoral studies, which he completed in March 1957. In February 1958, he joined the University of Delhi as a lecturer in physics and in April 1961 got promoted to readership. In August 1964, he left Delhi to take up a visiting professorship at
McMaster University in Hamilton, Ontario, Canada. In 1969 Pathria returned to Canada and, in addition to his other academic pursuits, continued to teach a variety of courses at the
University of Waterloo and the
University of Windsor. In 1972 the Pergammon Press, Oxford, published his classic text
Statistical Mechanics, which became an instant success on the international scene. In the early 1990s, when his new publishers (Butterworth-Heinemann) persuaded Pathria to produce a second edition of this text, he sought the help of Surjit Singh, a former student of his from the
Chandigarh days (who had also been a postdoctoral fellow with him at Waterloo during the years 1983–87). The result of this joint effort was a brand new edition of this book that came out in July 1996 and, like its predecessor, continued to be a bestseller. Pathria retired from the University of Waterloo in August 1998 and, soon thereafter, moved to the west coast of the US and became an adjunct professor of physics at the
University of California at San Diego, a position he continued to hold till 2010. In 2009, Pathria's newest publishers (Elsevier/Academic) prevailed upon him to produce a third edition of this book. He now sought the help of Paul Beale, of the
University of Colorado at Boulder, whose co-authorship resulted in another brand new edition in March 2011. Ten years later, in 2021, Pathria and Beale produced a fourth edition of this book. ==Research interests==