Hamish William McIntosh was born in Vancouver on January 13, 1920. He lived in Cleveland, Ohio and Montreal, Quebec as a child. He was educated in England at St Hugh's School, and then at Cambridge for his M.B. At McGill, he was the case reporter of the Medical Undergraduate Society 1942. He received his M.D.,C.M. from McGill University in 1943 and received the Alexander D. Stewart Memorial Prize. He interned at Montreal General Hospital after which he served as a RCAMC Medical Officer. From 1946 to 1947 he became resident at the Royal Victoria Hospital to train in Internal Medicine, Endocrinology and Metabolic Diseases. He was the Caverhill Research Fellow at McGill University Clinic from 1947-1949. He received his Fellowship in medicine from the Royal College of Physicians and Surgeons of Canada and Diploma in Internal Medicine and M.Sc (Experimental Medicine) from McGill University. In 1949, he was awarded the Osler Scholarship of the Canadian Medical Association and was on the Endocrine staff at the Cleveland Clinic. In 1950, he became director of the Clinical Investigation Unit at Shaughnessy Hospital, Vancouver, B.C. and remained in this position for 25 years. In 1951, he was appointed to clinical teaching faculty at UBC, becoming full Professor of Medicine in 1966 and then Emeritus Professor in 1985. He published over 100 scientific medical papers.

His grandfather, Dr. James McIntosh, was also a McGill graduate.