He first contested the South Australian House of Assembly electorate of Flinders for the Liberal and Country League at the state election in 1938, but lost to Edward Craigie, the candidate for the Single Tax League, after the distribution of preferences.
[1] In 1941, Pearson was elected for Flinders, defeating Craigie on preferences from the Labor candidate.
Even though he moved to Belair, and later Lower Mitcham near Adelaide and his mother's home, he won the 1947 and 1950 elections for Flinders,[2] and retained his interest and support for farming and rural interests in his electorate on the Eyre Peninsula.
His brother Glen won the by-election for the consequential vacancy in the seat of Flinders.
[1] Pearson held his Senate seat by winning elections in 1953 and 1958, until his death in 1961, after which the South Australian parliament appointed Gordon Davidson to replace him.