Educated in Scotland and Europe, J. J. Hardie also travelled throughout Europe with his father who was a master mariner. Arriving in Australia in 1911 at the age of seventeen, Hardie spent the next four years working as a stockman in Queensland, New South Wales and the Northern Territory.
With the declaration of the First World War, Hardie rode to Cloncurry, Queensland intent on joining the Australian Light Horse. He was rejected by the Australian military and so returned to the UK where he successfully enlisted in the 2nd King Edward's Horse in April 1915. Hardie served in the infantry, tanks and cavalry in France, India and the Middle East.
Hardie returned to Australia in 1920. He settled on the land where he established a career in the primary industries. He initially began growing bananas (1921-1925) near Tweed Heads (New South Wales) but following an outbreak of disease in his crop, his interest shifted to the wool industry. He learnt wool-classing and in 1926 joined the Grazier's Co-operative Shearing Co. Ltd. becoming highly regarded as a wool-classer. Hardie developed a reputation for having a sound understanding of the practical problems that confronted both stock owners and breeders. He regularly wrote articles which appeared in agricultural journals and in the Bulletin's 'Man on the Land' column; this material was later expanded and republished in the form of 'practical manuals'.
Hardie wrote four novels that drew on his experiences of life on the land and gained a 'wide readership' built on an appreciation of the authenticity underpinning his work. In the article 'J. J. Hardie, Observer of the Inland', James Devaney regards the novelist as noteworthy for his ability to write of 'what he knows' in books that created 'pictures' of 'life on the land in Australia (Southerly 16.1 (1955): 13-16). The first three of Hardie's novels combine autobiography and fiction with his earliest work, Cattle Camp (1932), recounting the station 'romance of a Scots-born bushman and his war experiences'. Intended as the first in an unfinished trilogy, his last novel, Pastoral Symphony (1939), has been described as his 'most ambitious'. While based on the author's knowledge of station life, the fictional story tells of two escaped convicts who successfully breed cattle and sheep in pastoral New South Wales.
Hardie married a New Caledonian, Marguerite (Margot) Ernestine Daly, in 1935. In 1951, while Hardie was recuperating from heart trouble, the couple decided to travel to New Caledonia. Hardie suffered a heart attack en route and died soon after arriving at the hospital in Noumea