Alston was elected a member of the Alabama House of Representatives from 1836 to 1837. He served in the Alabama Senate from 1839 to 1842. He returned to the Alabama House in 1843. He served at the national level when elected as a Whig to the Thirty-first Congress, holding office from March 4, 1849 to March 3, 1851. He was not a candidate for renomination in 1850 and resumed the practice of his profession. Now running as a Democrat, Alston again became a member of the Alabama House from 1855 to 1857.