In 1924, Jaeger entered Sydney University at the age of 16, studying engineering, mathematics, and physics, and earned a B.Sc.
He then spent two additional years at Cambridge University, completing Part II of the Mathematical Tripos and continuing with research in theoretical physics.
After the World War II, Jaeger returned to Tasmania as a senior lecturer and authored several books, including new editions of Operational Methods in Applied Mathematics (with Carslaw in 1948) and Conduction of Heat in Solids (with Carslaw in 1959).
In 1951, Jaeger was invited to chair the new Department of Geophysics at the Australian National University in Canberra.
Jaeger was married twice: first to Sylvia Rees, from whom he divorced in 1950, and later to Martha Elizabeth (Patty) Clarke.