Hilmar Guðjónsson became a member of the cast of Reykjavik City Theater as soon as he graduated from the Iceland Academy of the Arts in 2010. Before, at the age of 20, he had played the role of Billy in Edwards Albees The Goat, who is Sylvia. Since graduation the roles have varied quite a lot. For example Trinkulo in The Tempest, Simon in The Seagull, Scarecrow in The Wizard of Oz, Alexander in Ingmar Bergmans Fanny and Alexander, George in Richard III and Ken in Red which he got the Icelandic Theater award for.
Hilmar has also played a part in a couple of films; Mr. Bjarnfredarson and Either way a part which he got nominated for at the Icelandic TV and Film Awards. In TV he has played a part in Fólkið í blokkinni, Fish out of Water, Stella Blómkvist and Venjulegt fólk as well as a lot of smaller parts, commercials and short films.
In 2012 Hilmar was awarded as a Shooting Star by the European Film Promotion.