Educated at Clongowes Wood College, Trinity College, Dublin, and the King's Inns, O'Connell was then called to the bar, but did not practice. In 1843, O'Connell was tried with his father in the State Trials, and was imprisoned in Richmond prison before being released the next year by an order of the House of Lords. During his father's declining years, he was the dominant force in the Repeal Association and denounced Young Ireland as irreligious and lawless.
In 1847, he closed down Conciliation Hall, and in 1848 reacted to the Rising by establishing closer links with the government. Of Daniel's four sons, he was considered to be the only one who inherited something of his father's political skill: he was nicknamed "The Young Liberator", although critics claimed he did little to justify the title. In 1851, he took part in the downfall of Lord John Russell and the Whigs from government.
After being censured by his constituency, he resigned his seat by taking the Chiltern Hundreds. He opposed the Tenant League and was subsequently elected as member for Clonmel in 1853, after which he accepted a sinecure position in the Hanaper Office at Dublin Castle. O'Connell was not an impressive public speaker, but wrote political works for the Repeal Association.
[11th United Kingdom Parliament. 12th United Kingdom Parliament. 13th United Kingdom Parliament.
14th United Kingdom Parliament. 15th United Kingdom Parliament]
He served in the United Kingdom Parliament as Member of Parliament for Youghal from 1832 to 1837, for Athlone from 1837–1841, for Kilkenny from 1841–1847, for Limerick from 1847–1851 and for Clonmel from 1853-57.