 The son of merchant and politician Richard O'Dwyer (1811 - 1875), a native of Waterford, Ireland and Wilhelmina Harton (1822 - 1887), a native of Banagher, Ireland, he was born in St. John's and moved to England with his family in 1868, his father looking after the importing side of the family's business and leaving the Newfoundland side of the business to be run by his younger brother, John (1813 - 1878).O'Dwyer returned to St. John's at the age of 21, after the death of his unmarried uncle John, to take over the family business with his brother John.He served in the Newfoundland cabinet as Receiver General from 1890 to 1893.