Gardom was born in Banff in 1924, studied law at UBC and practiced in Vancouver before turning to a career in politics.
He was first elected as a Liberal MLA in 1966, and joined the Social Credit party in 1974.
He was appointed to cabinet by then-premier Bill Bennett in 1975, and held several positions including attorney general and government house leader.
In 1995 he was appointed B.C.'s 26th lieutenant-governor and served until 2001.
He is survived by his wife of 57 years, Helen Eileen Mackenzie, their five children and 11 grandchildren. The cause of death has not yet been released.
B.C. Premier Christy Clark said Gardom had a unique ability to draw people to him through his dedication to public service.
"As an MLA, cabinet minister, British Columbia's agent in London or the Queen's representative in British Columbia, Garde possessed a unique gift: the ability to draw people to him because they understood his dedication to public service was based on a true love of making life better for those he served.
"An iconoclast, Garde was an inspiration to a generation of those serving the public. His irreverent spirit ensured British Columbians never felt isolated, but rather an integral part of the process."
Gardom also helped lead the fight against impaired driving, noted Clark.
"His CounterAttack against Drinking and Driving initiative saved countless lives throughout B.C," said Clark.
The government says flags will be lowered to half-mast at all B.C. government buildings in tribute to Gardom and his more than four decades of public service.