 Casson was educated at Latymer Upper School and Trinity College, Cambridge, where he graduated with a BA in the Mathematical Tripos in 1965.His doctoral advisor at the University of Liverpool was C. T. C. Wall, but he never completed his doctorate; instead what would have been his Ph.D. thesis became his fellowship dissertation as a research fellow at Trinity College.Casson was Professor of Mathematics at the University of Texas at Austin between 1981 and 1986, at the University of California, Berkeley, from 1986 to 2000, and has been at Yale since 2000.