He was educated at Leigh Grammar School, going on to study at the University of Manchester, graduating in 1915 with a first-class honours degree in mathematics.

[13] Following service with the Royal Flying Corps during World War I, where he trained as a pilot, he studied for a Doctorate of Science (DSc) degree in Mathematics at Manchester, graduating in 1922.

On the advice of Sydney Chapman, he then successfully applied for a Senior 1851 Exhibition at Trinity College, Cambridge, where he was supervised by Ralph H. Fowler and graduated with a second doctorate in 1924.

Holding the first Chair of Theoretical Chemistry in the United Kingdom (at the University of Cambridge), he established a research school applying to phenomena in physics and organic chemistry new concepts of quantum mechanics and the interactions of subatomic particles.

Also named after him, the Lennard-Jones Laboratory houses the School of Chemistry and Physics at Keele University.

Keele University holds a collection of Lennard-Jones's published work, as well as a laboratory named in his honour.