T.J. Harrison was born in Graysville, Manitoba and after his public schooling, in the fall of 1906, he became the first student to register at the new Manitoba Agricultural College. Following graduation, he was retained by the college as an instructor in field husbandry until 1913, when he was made superintendent of the Dominion Experimental Farm at Indian Head, Saskatchewan.

In 1915, he returned to Winnipeg to accept the position of professor of field husbandry at the college, with the stipulation that he be permitted to undertake and expand experimental work in agronomy. His research concentrated on crossbreeding and selection of high yielding, six row barley suited to the malting industry. Professor Harrison designed and constructed the first barley malt laboratory for research in Canada.

In 1920, Professor Harrison was instrumental in founding the Manitoba Agronomists Conference. Leaving the college in 1925, he became assistant commissioner for Manitoba on the Board of Grain Commissioners. During his tenure with the board, he was also president of the Canadian Seed Growers Association. In 1932, he was appointed chairman of the National Barley Committee and was instrumental in forming the Barley Improvement Institute, now known as the Brewing and Malting Research Institute.

An active member of the Kiwanis Club of Winnipeg for 33 years, he organized a public speaking competition open to members of the Boys and Girls Clubs of Manitoba. This competition is still in existence today and the Harrison Shield is awarded annually to the winner of the provincial 4-H Public Speaking Competition.

Harrison was elected a Fellow of the Agricultural Institute of Canada and a Member of the Royal Academy. In 1952, in recognition of his major contributions to agriculture in Western Canada, the University of Manitoba bestowed an Honorary Doctorate of Laws upon him.