Being an Associate Artist with the Royal Shakespeare Company, Masson trained at Royal Scottish Academy of Music and Drama as well as obtaining a BA in Dramatic Studies. His television debut came in 1987 in the television series City Lights appearing as Crawford Minty. He then went on to appear in Taggart, Red Dwarf, My Dead Dad, The Brown Man and Paris before landing a significant role The High Life.
Since his departure from EastEnders and many other television shows, Masson has gone on to work on other shows such as Gypsy Woman and Doctors. It appears that Masson has a higher interest in theatre, as he has been involved in many productions varying from Macbeth and The Lion, the Witch and the Wardrobe. He has also written a series of Scottish musicals; Stiff!, Mince and Pants.