He began his acting career in 1975 with a summer stock company formed with fellow Guelph students that played Muskoka resorts.[6] He subsequently worked as a stage carpenter and scene painter in Toronto.[6]
He met actress Sheila McCarthy in 1983 while working in theatre in London, Ontario, and they were married in December 1986 in Stratford.[3] The couple had two daughters.[3]
In 2009, Donaldson was diagnosed with lung cancer, and while undergoing treatment continued to rehearse and perform as an actor. He would often have chemotherapy in the morning and work in the evenings. Writer George F. Walker said, "He had such great energy – he never made you feel like he needed special treatment".[3] Roles during this period included acclaimed performances in Glengarry Glen Ross at the Soulpepper Theatre, 'Art' at Canadian Stage and Walker's And So It Goes at Factory Theatre.[3][8] Donaldson died of lung cancer at Princess Margaret Hospital in Toronto at the age of 57.[2][3] The director of the Stratford Festival, Antoni Cimolino, described Donaldson as "the finest actor's actor. He was deeply admired for the conviction he brought to his work and the unsparing truth of his portrayals. He was versatile and able to give outstanding performances in modern plays, musicals and classics. But his home was Shakespeare."[4]
Canadian Film Awards 1968-1978, Genie Awards 1980-2011, Canadian Screen Awards 2012-present. Separate awards were presented by gender prior to 2022; ungendered awards for best performance regardless have been presented since.