Opperman joined the Liberal Party of Australia after the war and in 1949 was elected to the Parliament of Australia for the Victorian electorate of Corio centred on Geelong.
 He beat a senior Labor minister, J. J. Dedman and held the seat for 17 years before appointment to High Commissioner for Malta.

He became the Government Whip in 1955.
 He was appointed Minister for Shipping and Transport, a Cabinet position, in 1960.
 Between December 1963 and December 1966 he was Minister for Immigration (retaining the position when Harold Holt succeeded Sir Robert Menzies as Prime Minister).
 He oversaw a relaxation of conditions for entry into Australia of people of mixed descent and a widening of eligibility for well-qualified people.
 One assessment said: "He was the perfect party man: unswervingly loyal, safe with secrets, an honest adviser and a shoulder for fellow ministers to cry on, sometimes literally.
He made no pretence of statesmanship."

The assessment added:
He found the [opposition] Labor Party's socialist platform of the day too close to communism to allow any compromise.
His dedication to hard work left him with little sympathy for organised labour in any form, and probably inspired one of his campaign slogans 'Opperman for the Working Man.'
His autobiography, Pedals, Politics and People (1977), showed that – like his political idol, Menzies – he was a lover of tradition, European pageantry, and decorous manners.
He never quite forgave Harold Macmillan for forgetting, during a visit to Corio, to give proper thanks for a rug specially woven by local mills in the Macmillan tartan.

Opperman became Australia's first High Commissioner to Malta in 1967, a job he held for five years.
Opperman joined the Liberal Party of Australia after the war and in 1949 was elected to the Parliament of Australia for the Victorian electorate of Corio centred on Geelong.  He beat a senior Labor minister, J. J. Dedman and held the seat for 17 years before appointment to High Commissioner for Malta.
He became the Government Whip in 1955.  He was appointed Minister for Shipping and Transport, a Cabinet position, in 1960.  Between December 1963 and December 1966 he was Minister for Immigration (retaining the position when Harold Holt succeeded Sir Robert Menzies as Prime Minister).  He oversaw a relaxation of conditions for entry into Australia of people of mixed descent and a widening of eligibility for well-qualified people.  One assessment said: "He was the perfect party man: unswervingly loyal, safe with secrets, an honest adviser and a shoulder for fellow ministers to cry on, sometimes literally. He made no pretence of statesmanship." 
The assessment added:
He found the [opposition] Labor Party's socialist platform of the day too close to communism to allow any compromise. His dedication to hard work left him with little sympathy for organised labour in any form, and probably inspired one of his campaign slogans 'Opperman for the Working Man.' His autobiography, Pedals, Politics and People (1977), showed that – like his political idol, Menzies – he was a lover of tradition, European pageantry, and decorous manners. He never quite forgave Harold Macmillan for forgetting, during a visit to Corio, to give proper thanks for a rug specially woven by local mills in the Macmillan tartan.
Opperman became Australia's first High Commissioner to Malta in 1967, a job he held for five years.
Hubert Opperman