Mackenzie grew up in Melbourne, where his father John was a land and estate agent.
Himself an agent, dealer and journalist, Harold Mackenzie was well educated and widely travelled, and spent some time in the late 1800s travelling through the Riverina, visiting the freehold stations of the time and recording information about the country, its stock, its farmers, its challenges and its problems. Fifty-one articles which he wrote for the Hay newspaper, The Riverina Grazier, in 1893 and 1894, have been republished in Mackenzie's Riverina: A Tour of the Hay District Pastoral Holdings in the 1890s (Hay Historical Society, 2002), which includes some of his poems. He also wrote on pastoralists and producers of the Hunter Valley region for the Maitland Mercury, 1894 to 1897.
Mackenzie never married. He died at sea of tuberculosis two days out of Melbourne, on a return voyage from Ceylon.
