Hewitt was born in Spanish Town, Jamaica, educated in Bath, England, and practiced law in Jamaica until the death of his father in 1850. He came to Canada and settled in Barrie, Upper Canada, where he became part of local society. In 1854, he brought his mother and sister Agnes to live with him. About that time he joined the local militia and eventually gained the rank of lieutenant-colonel.
Bernard was a successful lawyer and co-editor of the Upper Canada Law Journal when he became Attorney General John A. Macdonald's private secretary in 1857. He soon became chief clerk. He was the recording secretary at the Charlottetown Conference. In February 1867, Hewitt's sister Agnes married John A. Macdonald and became Agnes Macdonald, 1st Baroness Macdonald of Earnscliffe. He was also very good friends with John A. Macdonald before he became his brother-in-law.
In 1872, he was made a Companion of the Order of St Michael and St George.
- Robert Alexander Harrison; Peter Oliver; Osgoode Society for Canadian Legal History (1 October 2003). The conventional man: the diaries of Ontario Chief Justice Robert A. Harrison, 1856-1878. University of Toronto Press. p. 627. ISBN 978-0-8020-8842-0.
- "Hewitt Bernard". Dictionary of Canadian Biography (online ed.). University of Toronto Press. 1979–2005.
- Ontario Historical Plaques - Hewitt Bernard