Whelan died at the age of 88 on Tuesday night from complications from a stroke.
A crowd of friends, family and political dignitaries packed into the St. John The Baptist Church in his southwestern Ontario hometown of Amherstburg to pay respects to Whelan.
Whelan served as then-prime minister Pierre Trudeau's agriculture minister between 1972 to 1984.
Among the Liberal heavyweights attending the service was former prime minister Jean Chretien, who sat in the Trudeau cabinet with Whelan and appointed him to the Senate in 1996.
Chretien told reporters that Whelan's journey from a small-town farmer to outspoken cabinet minister was a Canadian success story.
He said Whelan never slipped from his commitment to his constituents and farmers during talks in cabinet.
"He came from a very poor family and he had known misery in his life, and he was around the table and talking for the small person."
Beside the casket sat Whelan's green cowboy hat, an unmistakable trademark of a man known for his folksy personality.
In a eulogy, former Liberal cabinet minister Herb Gray remembered arriving in Ottawa with Whelan when they were both elected to Parliament in 1962 representing ridings in nearby Windsor.
Gray — who shared a Parliament Hill office with Whelan no bigger than a "broom closet" — said Whelan was a one-of-a-kind character recognized from coast to coast.
"There was no personality like him in Canada, and most of all he was committed to his community and his country," Gray told the crowd.
"He will not be just missed, he will be long remembered."
Gray said Whelan was steadfast when it came to standing up for the interests of Canadian farmers.
"He was devoted to the flourishing of Canadian agriculture and to supply management," Gray said.
And he fondly recalled how "that giant of a personality, the man in the green Stetson hat" never shied from speaking his mind.
"We were in cabinet together and believe me, he always spoke up."
Whelan's 12-year stint as agriculture minister was interrupted only for nine months in 1979-80 when the Conservatives took office.
He took a run at the Liberal leadership in 1984, and in an attempt to sway delegates put his outsized personality on display, declaring "I don't think there is any politician that is as well known in the world as I am."
They weren't won over. Whelan finished last among the seven candidates in the race.
Eugene Francis Whelan was born July 11, 1924, in Amherstburg, a small town near Windsor. His father, a farmer and municipal politician, died when he was six, and the family lost the farm and struggled to weather the Great Depression.
At 16, Whelan quit school and spent some time as a tool-and-die maker before returning to farming.
At 21 he was a surprise winner of a school board election. He went on to become reeve and warden of Essex County before being elected to Parliament.
— By Will Campbell in Toronto
(CKLW, The Canadian Press)